1. Electrons and Reactivity
סידור האלקטרונים באטומים
Electrons and Reactivity
Atoms contain
a very small nucleus packed with neutrons and positively charged protons.
a large volume of space around the nucleus that contains the negatively charged electrons.
It is the electrons that determine the physical and
chemical properties of atoms.

2. Electron Energy Levels
רמות אנרגיה של אלקטרונים
Electron Energy Levels
Electrons surround the nucleus in specific energy levels.
Each energy level has a principal quantum number (n).
The lowest energy level, which is closest to the nucleus, is labeled n = 1.
The second-lowest energy level is labeled n = 2
The third n = 3, and so on.
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3. Figure: 09-09
Title:
The Bohr model of the atom, showing electron orbits

4. רמות אנרגיה של אלקטרונים
Electron energy levels increase
in energy and number as
electrons get farther away from
the nucleus.
The higher the electron energy
levels,
the more electrons they hold.
the more energy the electrons have.
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5. תת רמות Within each energy level, we have sublevels that
contain electrons with identical energy.
are identified by the letters s, p, d, and f.
The number of sublevels within a given energy level
is equal to the value of the principal quantum number, n.
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6. Energy Levels and Sublevels, Continued
The first energy level has one sublevel designated 1s.
The second energy level has two sublevels designated 2s and 2p.
The third energy level has three sublevels designated 3s, 3p, and 3d.

7. רמות אנרגיה ותת רמות Figure: 09-19 Title:
Shells are organized into subshells

8. Energy Levels and Sublevels
רמות אנרגיה ותת רמות
Energy Levels and Sublevels
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9. Energy of Sublevels האנרגיה בתת הרמות Within any energy level,
the s sublevel has the lowest energy.
the p sublevel follows and is slightly higher in energy.
the d sublevel follows the p and is slightly higher in energy than the p.
the f sublevel follows the d and is slightly higher in energy than the d.
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10. אורביטלים Each electron sublevel consists of orbitals, which
are regions where there is the highest probability of finding an electron.
have their own unique three-dimensional shape.
can hold up to 2 electrons.
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11. s Orbitals We know that s orbitals have a spherical shape,
centered around the atom’s nucleus.
The s orbitals get bigger as the principal quantum number, n, gets bigger.
The s orbitals can hold up to 2 electrons that must spin in opposite directions.
n = 1
n = 2
n = 3
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12. s orbitals · spherical in shape Electron density map
Representation of volume of orbital

13. Figure: 09-20
Title:
Comparison of 1s and 2s orbitals

14. Quantum Mechanical Model of the Atom
An orbital is the region of space where there is a high probability of finding an atom.
In the quantum mechanical atom, orbitals are arranged according to their size and shape.
The higher the energy of an orbital, the larger its size.
All s orbitals have spherical shapes.

15. p Orbitals There are three p orbitals in each energy level,
starting with energy level 2. They
have a two-lobed shape, much like tying a balloon in the middle, and can hold 2 electrons.
are labeled x, y, and z.
increase in size as the value of n increases.
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16. Location of Electrons in an Orbital
The orbitals are the region of space in which the electrons are most likely to be found.
An analogy for an electron in a p orbital is a fly trapped in two bottles held end to end.

17. Shapes of d Orbitals Recall that there are five different d sublevels.
Four of the d orbitals have a clover-leaf shape and one has a dumbbell and doughnut shape.

18. f orbitals
Complex shapes
7 different orientations

19. Sublevels and Orbitals
תת רמות ואורביטלים
Sublevels and Orbitals
Each sublevel consists of a specific number of orbitals.
An s sublevel contains one s orbital.
A p sublevel contains three p orbitals.
A d sublevel contains five d orbitals.
An f sublevel contains seven f orbitals.
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20. כמות האלקטרונים בכל רמה
Energy levels have a maximum number of electrons equal to 2n2.
Energy level Maximum number of electrons
n = 1 2(1)2 = 2(1) = 2
n = 2 2(2)2 = 2(4) = 8
n = 3 2(3)2 = 2(9) = 18

21. כמות האלקטרונים בתת הרמות
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22. סידור האלקטרונים של 20 יסודות ברמות האנרגיה