HW # 2: The Structure of the Atom WS

Aim 2: How can we describe the structure of the atom?

What is an atom?

1. The Atom Atoms are the basic building blocks of matter that make up everyday objects.

What do you know about the hydrogen atom?

Hydrogen Atom

What subatomic particles do you know?

What is the charge of the nucleus? What is the charge of the atom? In the nucleus are two subatomic particles:

2. Subatomic Particles Electrons and Nucleons. Nucleons: Protons Neutrons - + + -

What is the mass of the neutron and Proton What is the mass of the neutron and Proton? What is the charge of the the proton and neutron?

What is the mass of an electron?

In which table do you find the subatomic particles?

Proton Neutron Electron CHARGE Positive None Negative MASS 1 a.m.u. 1 a.m.u 1/1836 a.m.u LOCATION Nucleus orbiting around the nucleus 1 1 1 -1

3. The Mass Number The mass number is not a mass! It is, however, very nearly the same as the mass of the atom in atomic mass unit. The mass number = # protons + # neutrons Atomic mass 6.941 Li 3 7 Li 3 Mass Number

How do you find the number of neutrons of lithium?

4. Number of Neutrons # of neutrons = the mass number – atomic number Mass number 7 Li 3 - Atomic number 4 # neutrons

Which number do you use to identify Carbon in the periodic table?

5. Atomic Number Li 3 Identify an element This # never change! p = 3 e- = 3 Charge of the nucleus= +3 7 Li 3 Atomic Number = # protons = # of electrons

The atomic number is very important because it tells you the number of : Protons in the atom! Electrons in the atom!

6. Electron Configuration It shows how many electrons are in each principal energy level. See periodic table. 7 Li 3 2-1 Electron configuration

Electron Configuration: 2-4

Electron Configuration Periodic Table Atomic Number Number of Protons Number of Neutrons Number of Electrons Mass Number Name of the element Electron Configuration 6 12 carbon 2-4

Electron Configuration Periodic Table Atomic Number Number of Protons Number of Neutrons Number of Electrons Mass Number Name of the element Electron Configuration 11 12 23 sodium 2-8-1

Electron configuration: 2-8-1

Electron Configuration Periodic Table Atomic Number Number of Protons Number of Neutrons Number of Electrons Mass Number Name of the element Electron Configuration 19 20 39 2-8-8-1

Electron Configuration Periodic Table Atomic Number Number of Protons Number of Neutrons Number of Electrons Mass Number Name of the element Electron Configuration 17 18 35 2-8-7

Electron configuration: 2-8-7

2 10 Atomic Number # of Protons # of Neutrons # of Electrons Mass # Name of the element Electron Configuration 2 10

Electron Configuration Atomic Number Number of Protons Number of Neutrons Number of Electrons Mass Number Name of the element Electron Configuration 2 10 Neon 2-8 19 8 2-6 16 32 sulfur 1 26 2-8-14-2

7 2-5 27 Cobalt 2-8-15-2 16 2-8-6 6 Carbon 12 17 2-8-7 18 23 Atomic Number Number of Protons Number of Neutrons Number of Electrons Mass Number Name of the element Electron Configuration 7 2-5 27 Cobalt 2-8-15-2 16 2-8-6 6 Carbon 12 17 2-8-7 18 23

8. The Bohr Model of the Atom Niels Bohr proposed a model of the atom in which the electrons move around the nucleus on fixed orbits.

PE INCREASES Low-energy electrons orbit closer to the nucleus High-energy electrons orbit farther to the nucleus 1 2 3 4 5 6 7 PE INCREASES

Lithium Boron Copper Calcium

9. Excited state and Ground state When energy is added to atoms, the electrons move to a higher energy level called the excited state. Because nature prefers a lower energy state, the electrons gives off their added energy in the form of light. This allows the electrons to return to their ground state

Electron Waves and Orbits When an electron "jumps" from one orbit (energy level) to another, the difference in energy between the two orbits is hf, where h is Planck’s constant and f is the frequency of the emitted or absorbed light. Electron Waves and Orbits

7 3Li 2-1

7 3 Li 2-1 Energy is absorbed

Excited State 7 3 Li 1-2

Ground State 7 3 Li 2-1 Energy is released

Lithium

Reading The light given off from an excited element can be passed through a prism or diffraction gradient to determine the exact wavelengths of light being given off by the excited electron. These exact wavelengths of light are what we called an element ‘s line spectrum.

10. Bright-Line Spectra or Fingerprints of Elements: Each element has its own distinct line spectra. Helium line spectra

Line Spectra for Hydrogen, Mercury, and Neon Hg Ne

Excited State unstable and drops back down Spectrum Excited State n=4 UV Excited State n=3 Excited State unstable and drops back down Excited State Vi s ible But only as far as n = 2 this time n=2 Energy released as a photon Frequency proportional to energy drop IR n=1 Ground State

Atomic Spectra An absorption spectrum consists of the various frequencies absorbed by a substance when white light is passed through it. The frequencies in the spectrum of an element fall into sets called spectral series. Seen here is the spectral series of hydrogen.

End of the show!!!!

1. Where do we find most of the mass of an atom?   In the outer part of an atom In the electron energy levels (shells) In the nucleus

2. Which two sub-atomic particles make up most of the mass of an atom? Neutrons   Electrons   Protons

3. Chlorine atoms have 17 electrons 3. Chlorine atoms have 17 electrons. What is the electronic structure of an atom of chlorine?   10-7 2-8- 7 2-10-5 2-7-8  

4. Which represents a metal?

5. Which represents lithium?  

6. Which represents oxygen?

7. Which atom has six electrons in its outer shell?

8. What is the electronic structure of an atom of lithium? 3 2-1 1-2 1-1-1  

9. Which atom contains eight protons?

10. What is the electronic structure of an atom of neon? 2-8 2-4-4 8-2

11. What is the electronic structure of an atom of phosphorus ? 105 2-8-5 2-5-8 5-8-2

12. What is the electronic structure of an atom of potassium ? 2-8-9 2-8-8-1 2-8-7-2 1-8-8-2