The Wave Nature of Light

The Wave Nature of Light
A wave is a continuously repeating change or oscillation in matter or in a physical field. Light is a wave, consisting of oscillations in electric and magnetic fields, traveling through space. 7- מבנה האטום

A wave can be characterized by its wavelength and frequency. Wavelength, symbolized by the Greek letter lambda, l, is the distance between any two identical points on adjacent waves. Frequency, symbolized by the Greek letter nu, n, is the number of wavelengths that pass a fixed point in one unit of time (usually a second). The unit is 1/S or s-1 which is also called the Hertz (Hz). 7- מבנה האטום

c = nl The Wave Nature of Light
Wavelength and frequency are related, their product equals to speed of light. The speed of light, c, is x 108 m/s. c = nl When the wavelength is reduced by a factor of two, the frequency increases by a factor of two. 7- מבנה האטום

What is the wavelength of blue light with a frequency of 5.09 1014/s? n = 5.09  1014/s c = 3.00  108 m/s c = nl so l = c/n 7- מבנה האטום

E increasing,  increasing,  decreasing
Electromagnetic Radiation E increasing,  increasing,  decreasing The range of frequencies and wavelengths of electromagnetic radiation is called the electromagnetic spectrum. 7- מבנה האטום

Quantum Effects and Photons
Light consists of quanta(singular: quantum) or particles of electromagnetic energy, called photons. The energy of each photon is proportional to its frequency: E = hn h =  10−34 J  s (Planck’s constant) Light, therefore, has properties of both waves and matter. Neither understanding is sufficient alone. This is called the wave-particle duality of light. 7- מבנה האטום

Photons Photons with λ = 452 nm are blue.
What’s the frequency of this radiation? What’s the energy of 1 of these photons? What’s the energy of 1 mol of 452-nm photons? a) n = c c  n = = x 108 ms-1 452 x 10-9 m = 6.63 x 1014 s-1 b) E = hn E = x Js (6.63 x 1014 s-1) = 4.39 x J c) E/mol = 4.39 x J (6.022 x 1023 mol-1) = 2.6 x 105 J mol-1 7- מבנה האטום

Spectra When atoms or molecules absorb energy, that energy is often released as light energy. Fireworks, neon lights, etc. When that emitted light is passed through a prism, a pattern of particular wavelengths of light is seen that is unique to that type of atom or molecule; the pattern is called an emission spectrum. Noncontinuous Can be used to identify the material Flame tests 7- מבנה האטום

Exciting Gas Atoms to Emit Light
Light is emitted when gas atoms are excited via external energy (e.g., electricity or flame). Each element emits a characteristic color of light. 7- מבנה האטום

Emission Spectra 7- מבנה האטום

Examples of Spectra A line spectrum shows only certain colors or specific wavelengths of light. A continuous spectrum contains all wavelengths of light. 7- מבנה האטום

Identifying Elements with Flame Tests
Na K Li Ba 7- מבנה האטום

Rydberg’s Spectrum Analysis
Johannes Rydberg (1854–1919) Rydberg analyzed the spectrum of hydrogen and found that it could be described with an equation that involved an inverse square of integers. m: shell the transition is to (inner shell) l 1 = R n2 m2 − R= X 10-2 nm-1 n: shell the transition is from (outer shell) 7- מבנה האטום

The Bohr Theory of the Hydrogen Atom
In 1913, Neils Bohr, a Danish scientist, set down postulates to account for: 1. The stability of the hydrogen atom. 2. The line spectrum of the atom. 7- מבנה האטום

Energy-Level Postulate
An electron can have only specific energy values called energy levels. Energy levels are quantized. Energy levels of the hydrogen atom can be determined using the formula: RH =  10−18 J (Rydberg constant) n = principal quantum number 7- מבנה האטום

Transitions Between Energy Levels
An electron can change energy levels by absorbing energy to move to a higher energy level or by emitting energy in the form of a photon to move to a lower energy level. 7- מבנה האטום

Atomic Spectroscopy Explained
Each wavelength in the spectrum of an atom corresponds to an electron transition between orbitals. When an electron is excited, it transitions from an orbital in a lower energy level to an orbital in a higher energy level. When an electron relaxes, it transitions from an orbital in a higher energy level to an orbital in a lower energy level. When an electron relaxes, a photon of light is released whose energy equals the energy difference between the orbitals. 7- מבנה האטום

Electron Transitions To transition to a higher energy state, the electron must gain the correct amount of energy corresponding to the difference in energy between the final and initial states. Electrons in high energy states are unstable and tend to lose energy and transition to lower energy states. Each line in the emission spectrum corresponds to the difference in energy between two energy states. 7- מבנה האטום

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Bohr Model of H Atoms For a hydrogen electron, the energy lost is given by: If ni is the principal quantum number for of the initial energy level , and nf is the principal quantum number of the final energy level, then,  7- מבנה האטום

Bohr Model of H Atoms In general, hv equals –ΔE: That is,
Recalling that v = c/λ, the above equation can be written as: 1 𝜆 = 𝑅 𝐻 ℎ𝑐 𝑛 𝑓 − 1 𝑛 𝑖 2 7- מבנה האטום

Bohr Model of H Atoms Light is absorbed by an atom when the electron transition is from lower n to higher n (nf > ni). In this case, DE will be positive. Light is emitted from an atom when the electron transition is from higher n to lower n (nf < ni). In this case, DE will be negative. An electron is ejected when nf = ∞. 7- מבנה האטום

Bohr Model of H Atoms Energy-level diagram for the electron in the hydrogen atom. 7- מבנה האטום

Bohr Model of H Atoms Electron transitions for an electron in the hydrogen atom. 7- מבנה האטום

Bohr Model of H Atoms Determine the wavelength of the light emitted when the electron in a hydrogen atom undergoes a transition from n = 4 to n = 2 It is known that: Subtracting the lower value from the higher value gives a positive result. If the result is negative, reverse the subtraction. 7- מבנה האטום

Bohr Model of H Atoms Equate the result to hν as it equals the energy of the photon. The frequency of the light emitted is: Since The color is blue-green. 7- מבנה האטום

Beyond Bohr: Quantum Mechanics
Bohr’s model predicts the H-atom: emission and absorption spectrum. ionization energy. The model does not work for any other atom. e- do not move in fixed orbits. 7- מבנה האטום

The Quantum Mechanical Model of the Atom
In 1926, Erwin Schrödinger proposed the quantum mechanical model of the atom, which focuses on the wavelike properties of the electron. In 1927, Werner Heisenberg stated that it is impossible to know precisely where an electron is and what path it follows—a statement called the Heisenberg uncertainty principle. 7- מבנה האטום

Probability of finding
The Quantum Mechanical Model of the Atom Probability of finding electron in a region of space (Y 2) Wave equation Wave function or orbital (Y) Solve Quantum mechanics allows us to make statistical statements about the regions in which we are most likely to find the electron. Solving Schrödinger’s equation gives us a wave function, represented by the Greek letter psi, y, which gives information about a particle in a given energy level. Psi-squared, y 2, gives us the probability of finding the particle within a region of space. 7- מבנה האטום

Wave Function The wave function for the lowest level of the hydrogen atom is shown to the left. 7- מבנה האטום

Two additional views are shown on the next slide.
Wave Function Two additional views are shown on the next slide. Figure A illustrates the probability density for an electron in hydrogen. Figure B shows the probability of finding the electron at various distances from the nucleus. The highest probability (most likely) distance is at 50 pm. 7- מבנה האטום

Wave Function A B 7- מבנה האטום

Quantum Numbers According to quantum mechanics, each electron is described by four quantum numbers: 1. Principal quantum number (n) 2. Angular momentum quantum number (l) 3. Magnetic quantum number (ml) 4. Spin quantum number (ms) The first three define the wave function for a particular electron. The fourth quantum number refers to the magnetic property of electrons. 7- מבנה האטום

Wave Function A wave function for an electron in an atom is called an atomic orbital (described by three quantum numbers—n, l, ml). It describes a region of space where there is high probability of finding the electron. 7- מבנה האטום

Principal Quantum Number, n
This quantum number is the one on which the energy of an electron in an atom primarily depends. The smaller the value of n, the lower the energy and, in some cases, the smaller the orbital. The principal quantum number can have any positive value: 1, 2, 3, . . . Orbitals with the same value for n are said to be in the same shell. 7- מבנה האטום

Angular Momentum Quantum Number, l
This quantum number distinguishes orbitals of a given n (shell) having different shapes. It can have any integer value from 0 to n –1. For a given n, there will be n different values of orbitals with a distinctive shape, l. Orbitals with the same values for n but different l are said to be in different subshells of a certain shell. 7- מבנה האטום

Quantum Numbers Subshells are sometimes designated by lowercase letters: ℓ code s 1 p 2 d 3 f 4 g 7- מבנה האטום

Magnetic Quantum Number, ml ,(mℓ = -ℓ to +ℓ )
This quantum number distinguishes orbitals of a given n and l—that is, of a given energy and shape but having different orientations. For l = 0, ml = 0. For l = 1, ml = –1, 0, and +1. Orbitals have the same shape but different orientations in space. ,(mℓ = -ℓ to +ℓ ) 7- מבנה האטום

Spin Quantum Number, ms This quantum number refers to the two possible orientations of the spin axis of an electron. It may have a value of either +1/2 or -1/2. 7- מבנה האטום

Summary of Quantum Numbers

Orbital Energies of the Hydrogen Atom

Quantum Numbers State whether each of the following sets of quantum numbers is permissible for an electron in an atom. If a set is not permissible, explain why. n = 1, l = 1, ml = 0, ms = ½ n = 3, l = 1, ml = –2, ms = –1/² c. n = 2, l = 1, ml = 0, ms = ½ d. n = 2, l = 0, ml = 0, ms = 1 7- מבנה האטום

Quantum Numbers Not permissible
The l quantum number is equal to n. It must be lesser than n. b. Not permissible The magnitude of the ml number must not be greater than 1. c. Permissible d. Not permissible The ms quantum number can be only +1/2 or –1/2. 7- מבנה האטום

Probability and Radial Distribution Functions
y 2 is the probability density. The probability of finding an electron at a particular point in space For s orbital maximum at the nucleus Decreases as you move away from the nucleus The radial distribution function represents the total probability at a certain distance from the nucleus. Maximum at most probable radius Nodes in the functions are where the probability drops to 0. 7- מבנה האטום

Probability Density for s Orbitals (l = 0)
The probability density function represents the total probability of finding an electron at a particular point in space. 7- מבנה האטום

Radial Distribution Function
The radial distribution function represents the total probability of finding an electron within a thin spherical shell at a distance r from the nucleus. The probability at a point decreases with increasing distance from the nucleus, but the volume of the spherical shell increases. The net result is a plot that indicates the most probable distance of the electron in a 1s orbital of H is 52.9 pm. 7- מבנה האטום

Each principal energy level has one s orbital.
l = 0, the s Orbital Each principal energy level has one s orbital. Lowest energy orbital in a principal energy state Spherical Number of nodes = (n – 1) 7- מבנה האטום

Probability Densities and Radial Distributions for 2s and 3s Orbitals

l = 1, p orbitals Each principal energy state above n = 1 has three p orbitals. ml = −1, 0, +1 Each of the three orbitals points along a different axis. px, py, pz The second-lowest energy orbitals in a principal energy state Two-lobed One node at the nucleus; total of n nodes 7- מבנה האטום

p Orbitals (l = 1) 7- מבנה האטום

l = 2, d Orbitals Each principal energy state above n = 2 has five d orbitals. ml = −2, − 1, 0, +1, +2 Four of the five orbitals are aligned in a different plane. The fifth is aligned with the z axis, dz squared. dxy, dyz, dxz, dx squared – y squared The third-lowest energy orbitals in a principal energy level Mainly four-lobed One is two-lobed with a toroid Planar nodes Higher principal levels also have spherical nodes. 7- מבנה האטום

d Orbitals (l = 2) 7- מבנה האטום

l = 3, f Orbitals Each principal energy state above n = 3 has seven f orbitals. ml = −3, −2, −1, 0, +1, +2, +3 The fourth-lowest energy orbitals in a principal energy state Mainly eight-lobed Some two-lobed with a toroid Planar nodes Higher principal levels also have spherical nodes. 7- מבנה האטום

f Orbitals (l = 3) 7- מבנה האטום

The Phase of an Orbital Orbitals are determined from mathematical wave functions. A wave function can have positive or negative values. As well as nodes where the wave function = 0 The sign of the wave function is called its phase. When orbitals interact, their wave functions may be in phase (same sign) or out of phase (opposite signs). This is important in bonding. 7- מבנה האטום

Phases 7- מבנה האטום

Electron configuration and orbital diagram
An electron configuration of an atom is a particular distribution of electrons among available subshells. An orbital diagram of an atom shows how the orbitals of a subshell are occupied by electrons. Orbitals are represented with a circle ( or as a square) ; electrons are represented with arrows up for ms= +½ or down for ms= -½. ( or half-arrow) 7- מבנה האטום

The Pauli exclusion principle summarizes experimental observations that no two electrons in one atom can have the same four quantum numbers. That means that within one orbital, electrons must have opposite spin. It also means that one orbital can hold a maximum of two electrons (with opposite spin). 7- מבנה האטום

The Pauli exclusion principle
An s subshell, with one orbital, can hold a maximum of 2 electrons. A p subshell, with three orbitals, can hold a maximum of 6 electrons. A d subshell, with five orbitals, can hold a maximum of 10 electrons. An f subshell, with seven orbitals, can hold a maximum of 14 electrons. 7- מבנה האטום

Allowed Quantum Numbers

Determine which of the following orbital diagrams or electron configurations are possible and which are impossible. Provide explanations. a. b. c d. 1s32s1 e. 1s22s12p f.1s22s22p63s23p63d84s2 1s 2s 2p 1s 2s 2p 1s 2s 2p 7- מבנה האטום

Possible. Impossible; there are three electrons in the 2s orbital. Impossible; there are two electrons is a 2p orbital with the same spin. Impossible; there are three electrons in the 1s subshell. Impossible; there are seven electrons in the 2p subshell. Possible. The 3d subshell can hold as many as ten electrons. 7- מבנה האטום

Sublevel Splitting in Multielectron Atoms
The sublevels in each principal energy shell of hydrogen all have the same energy or other single electron systems. We call orbitals with the same energy degenerate. For multielectron atoms, the energies of the sublevels are split. Caused by charge interaction, shielding, and penetration The lower the value of the l quantum number, the less energy the sublevel has. s (l = 0) < p (l = 1) < d (l = 2) < f (l = 3) 7- מבנה האטום

Shielding and Effective Nuclear Charge
Each electron in a multielectron atom experiences both the attraction to the nucleus and the repulsion by other electrons in the atom. These repulsions cause the electron to have a net reduced attraction to the nucleus; it is shielded from the nucleus. The total amount of attraction that an electron feels for the nucleus is called the effective nuclear charge of the electron. 7- מבנה האטום

Penetration The closer an electron is to the nucleus, the more attraction it experiences. The better an outer electron is at penetrating through the electron cloud of inner electrons, the more attraction it will have for the nucleus. The degree of penetration is related to the orbital’s radial distribution function. In particular, the distance the maxima of the function are from the nucleus 7- מבנה האטום

Shielding and Penetration

Penetration and Shielding
The radial distribution function shows that the 2s orbital penetrates more deeply into the 1s orbital than does the 2p. The weaker penetration of the 2p sublevel means that electrons in the 2p sublevel experience more repulsive force; they are more shielded from the attractive force of the nucleus. The deeper penetration of the 2s electrons means electrons in the 2s sublevel experience a greater attractive force to the nucleus and are not shielded as effectively. 7- מבנה האטום

Effect of Penetration and Shielding
Penetration causes the energies of sublevels in the same principal level to not be degenerate. In the fourth and fifth principal levels, the effects of penetration become so important that the s orbital lies lower in energy than the d orbitals of the previous principal level. The energy separations between one set of orbitals and the next become smaller beyond the 4s. The ordering can therefore vary among elements, causing variations in the electron configurations of the transition metals and their ions. 7- מבנה האטום

Electron Configurations of Multielectron Atoms
Electron Configuration: A description of which orbitals are occupied by electrons Degenerate Orbitals: Orbitals that have the same energy level—for example, the three p orbitals in a given subshell Ground-State Electron Configuration: The lowest-energy configuration Aufbau Principle (“building up”): A guide for determining the filling order of orbitals 7- מבנה האטום

Rules of the aufbau principle: Lower-energy orbitals fill before higher-energy orbitals. An orbital can hold only two electrons, which must have opposite spins (Pauli exclusion principle). If two or more degenerate orbitals are available, follow Hund’s rule. Hund’s Rule: If two or more orbitals with the same energy are available, one electron goes into each until all are half-full. The electrons in the half-filled orbitals all have the same value of their spin quantum number. 7- מבנה האטום

Electron Energy Sublevels in the Order of Increasing Energy
This results in the following order: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f. 7- מבנה האטום

Subshell Filling Order
Increasing (n + ℓ ), then increasing n 7- מבנה האטום

Orbital-Filling Diagram H: 1s1 1s 1s He: 1s2 1s 2s Li: 1s2 2s1 N: 1s2 2s2 2p3 1s 2s 2p 7- מבנה האטום

Shorthand Configuration Na: 1s2 2s2 2p6 3s1 [Ne] 3s1 P: 1s2 2s2 2p6 3s2 3p3 [Ne] 3s2 3p3 K: 1s2 2s2 2p6 3s2 3p6 4s1 [Ar] 4s1 Sc: 1s2 2s2 2p6 3s2 3p6 4s2 3d1 [Ar] 4s2 3d1 Ar configuration 7- מבנה האטום

Anomalous Electron Configurations
Expected Configuration Actual Configuration Cr: [Ar] 4s2 3d4 [Ar] 4s1 3d5 Cu: [Ar] 4s2 3d9 [Ar] 4s1 3d10 Note: ½ filled and filled shells have extra stability 7- מבנה האטום

Ion Electron Configurations
Similar approach. Positive ion: remove one e- for each “+” Negative ion: add one e- for each “-” S2- (16 + 2) = 18 e- S [Ne] 3s2 3p4 S2- [Ne] 3s2 3p or [Ar] Rb+ (37 - 1) = 36 e- Rb [Kr] 5s1 Rb+ [Kr] or [Ar] 3d10 4s2 4p6 7- מבנה האטום

Transition-Metal Ions
ns e- are lost first. Fe [Ar] 3d6 4s2 → Fe2+ [Ar] 3d6 → Fe3+ [Ar] 3d5 Mn [Ar] 3d5 4s2 → Mn2+ [Ar] 3d5 → Mn4+ [Ar] 3d3 → Mn7+ [Ar] 7- מבנה האטום

Magnetic Properties of Atoms
Although an electron behaves like a tiny magnet, two electrons that are opposite in spin cancel each other. Only atoms with unpaired electrons exhibit magnetism. This allows for the classification of atoms based on their behavior in a magnetic field. 7- מבנה האטום

Magnetic Properties of Atoms
A paramagnetic substance is one that is weakly attracted by a magnetic field, usually as the result of unpaired electrons. A diamagnetic substance is not attracted by a magnetic field generally because it has only paired electrons. Na: [Ne] 3s1 Hg: [Xe]4f145d106s2 Fe3+ ions in Fe2O3 have 5 unpaired electrons. This makes the sample paramagnetic. 7- מבנה האטום

Valence Electrons Gilbert N. Lewis: e- are arranged in shells.
Periodicity: similar elements have equal numbers of e- in their outer shell. Outer-shell e- = valence electrons = e- in incomplete shells, and partially-filled d and f orbitals Inner e- = core electrons Noble gas core complete d and f orbitals 7- מבנה האטום

Valence Electrons Note: # of valence e- = A group #
atom configuration core valence N 1s2 2s2 2p [He] s2 2p3 Si 1s2 2s2 2p6 3s2 3p2 [Ne] s2 3p2 Se 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p4 [Ar] 3d s2 4p4 Mn 1s2 2s2 2p6 3s2 3p6 3d 5 4s [Ar] d 5 4s2 Note: # of valence e- = A group # 7- מבנה האטום

N Valence Electrons Lewis dot symbols: Example nitrogen
Dots represent valence e-. Usually only used for s- and p-block elements. N Example nitrogen 5 valence e- (group 5A) 7- מבנה האטום

Electron Configuration and the Periodic Table
The group number corresponds to the number of valence electrons. The length of each “block” is the maximum number of electrons the sublevel can hold. The period number corresponds to the principal energy level of the valence electrons. 7- מבנה האטום

Periodic Trends: Atomic Radii
An estimate of atomic size ½(homonuclear bond length) Cl = 99 pm Cl2 bond = 198 pm. C = 77 pm diamond bond =154 pm. Radii are additive. C-Cl in CCl4 is 176 pm long. From radii: ( ) = 176 pm. 7- מבנה האטום

Atoms grow in size down a group. Larger shell (larger n) added in each new row. Atoms shrink across a period e- add to the same shell. Size stays ~constant? No, p+ add to the nucleus. Larger charge pulls all e- in, shrinking the atom. Big Jump in size from noble gas to alkali metal A new shell (with larger n) is added. 7- מבנה האטום

Periodic Trends: Ionic Radii
Grp 1A Grp 2A Grp 3A Li 157 Li+ 90 Be 112 Be2+ 59 B 86 B3+ 41 Na 191 Na+ 116 Mg 160 Mg2+ Al 143 Al3+ 68 K 235 K+ 152 Ca 197 Ca2+ 114 Ga 153 Ga3+ 76 Rb 250 Rb+ 166 Sr 215 Sr+ 132 In 167 In3+ 94 A cation is smaller than its neutral atom. Main block: outer shell completely removed. e-/e- repulsion reduced (fewer e- ). 7- מבנה האטום

Periodic Trends: Ionic Radii
Group 6A Group 7A O 74 O2- 126 F 72 F- 119 S 104 S2- 170 Cl 99 Cl- 167 Se 117 Se2- Br 114 Br- 182 Te 137 Te2- 207 I 133 I- 206 An anion is larger than its neutral atom. More e-/e- repulsion (more e-). The shell swells. 7- מבנה האטום

Ionic Radii Isoelectronic Ions O2- F- Na+ Mg2+ Ionic radius (pm) 126
Ne configuration Isoelectronic Ions O2- F- Na+ Mg2+ Ionic radius (pm) 126 119 116 86 Number of p+ 8 9 11 12 Number of e- 10 More p+ Smaller size 7- מבנה האטום

Ionization Energy Ionization Energy (Ei or I ): The amount of energy necessary to remove the highest-energy electron from an isolated neutral atom in the gaseous state 7- מבנה האטום

General Trends in First Ionization Energy
The larger the effective nuclear charge on the electron, the more energy it takes to remove it. The farther the most probable distance the electron is from the nucleus, the less energy it takes to remove it. First IE decreases down the group. Valence electron farther from nucleus First IE generally increases across the period. Effective nuclear charge increases 7- מבנה האטום

Periodic Trends: Ionization Energies
Down a group: IE ↓. Larger atom = less tightly held e- Across a period: IE ↑. Smaller atom = more tightly held e- 7- מבנה האטום

Exceptions in the First IE Trends
First ionization energy generally increases from left to right across a period. Except from 2A to 3A and 5A to 6A 7- מבנה האטום

Exceptions in the First Ionization Energy Trends, N and O
To ionize N, you must break up a half-full sublevel, which costs extra energy. When you ionize O, you get a half-full sublevel, which costs less energy. 7- מבנה האטום

Higher Ionization Energies
M+ + e– M + energy M2+ + e– M+ + energy M3+ + e– M2+ + energy 7- מבנה האטום

Trends in Successive Ionization Energies
Removal of each successive electron costs more energy. Shrinkage in size due to having more protons than electrons Outer electrons closer to the nucleus; therefore harder to remove There’s a regular increase in energy for each successive valence electron. There’s a large increase in energy when core electrons are removed. 7- מבנה האטום

Electron affinity (E.A.)
It is defined as the negative energy obtained when the neutral atom picks up an electron. When a stable negative ion forms, the quantity is positive. F(g) + e F-(g) 7- מבנה האטום

Electron affinities in the main-group elements show a periodic variation when plotted against atomic number, although this variation is somewhat more complicated than that displayed by ionization energies. In a given period, the electron affinity rises from the Group 1A element to the Group 7A element but with sharp drops in the Group 2A and Group 5A elements. Broadly speaking, the trend is toward more positive electron affinities going from left to right in a period. Let’s explore the periodic table by group. 7- מבנה האטום

All Group 1A elements have moderately positive electron affinities. Group 2A elements have a lesser electron affinity when compared to 1A elements. With the exception of the Group 5A element, the electron affinity tends to rise from the Group 2A element to the Group 7A element. No stable negative ions of the Group 8A elements have been found. 7- מבנה האטום

Group 5A generally lower EA than expected because extra electron must pair Groups 2A and 8A generally very low EA because added electron goes into higher energy level or sublevel 7- מבנה האטום

Octet Rule Octet rule: Main-group elements tend to undergo reactions that leave them with eight outer-shell electrons. That is, main-group elements react so that they attain a noble-gas electron configuration with filled s and p sublevels in their valence electron shell. Metals tend to have low Ei and low Eea. They tend to lose one or more electrons. Nonmetals tend to have high Ei and high Eea. They tend to gain one or more electrons. 7- מבנה האטום

Ionic Bonds and the Formation of Ionic Solids
1s2 2s2 2p6 3s1 1s2 2s2 2p6 3s2 3p5 Na + Cl Na+ + Cl– 1s2 2s2 2p6 1s2 2s2 2p6 3s2 3p6 7- מבנה האטום

The Wave Nature of Light

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