NAME: ________________________________________ AP Chemistry DUE DATE: JUNE 18TH SUMMER REV: Atomic Structure

Why?

Atoms and isotopes are identified by the numbers of protons, neutrons and electrons they contain. Before you

can understand the properties of atom, how atoms combine to form molecules, and the properties of molecules, you

must be familiar with the number of protons, neutrons and electrons associated with atoms.

The following activity will help you review the important structural characteristics of an atom.

SUCCESS CRITERIA:

Identify the composition of atoms and their isotopes in terms of the numbers of protons, neutrons, and

electrons.

Use atomic symbols to represent different atoms and their isotopes.

Determine the atomic number and mass number of an atom given an atomic/isotope symbol.

Determine the numbers of protons and neutrons given an atomic/isotope symbol.

MODEL 1: The Structure of the Atom

The subatomic particles that chemists are typically concerned with are the electron, the proton, and (to a lesser

extent) the neutron. The following table shows what distinguishes one subatomic particle from another:

Suppose we had a VERY powerful camera that allowed us to take the following ―snapshots‖ of atoms. A

snapshot is involved because the particles within the nucleus of an atom are in constant motion, as are the electrons in

space outside of the nucleus. To see what’s in the nucleus, we have to zoom in real close.

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Key Questions

1. How many protons are found in each of the following atoms/ions? 𝑁714 ______ 𝑁7

15 ______ 𝑁3−714 ______

2. How many neutrons are found in each of the following atoms/ions? 𝑁714 ______ 𝑁7

15 ______ 𝑁3−714 ______

3. How many electrons are found in each of the following atoms/ions? 𝑁714 ______ 𝑁7

15 ______ 𝑁3−714 ______

4. Based on the Model, what do all atoms (neutral or charged) of Nitrogen have in common?

5. Based on the Model, what do all atoms (neutral or charged) of Hydrogen have in common?

6. Look at the Periodic Table. What is the significance of the number (called the atomic number and represented by

the letter Z ) that appears above the symbol of each element on the periodic table? (Ex: H = 1, N = 7)

7. Based on your answer for #6, what do all Arsenic (As) atoms have in common?

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8. The number of what subatomic particle determines the identity of an atom?

9. The left-hand superscript in the symbol for an atom (e.g., the 2 in 𝐻12 ) is called the mass number and is represented

by the letter A. What subatomic particle(s) determine(s) the value of A?

10. Hydrogen-1, Hydrogen-2 and Hydrogen-3 are isotopes of the element Hydrogen. Nitrogen-14 and Nitrogen-15 are

isotopes of the element Nitrogen. What subatomic particle distinguishes isotopes of the same element from each

other?

11. If present, what does the right-hand superscript in the symbol for an atom (Ex: 2+ in 𝑀𝑔2+) tell the you?

12. Consider when an atom becomes an ion (Ex: N becomes 𝑁3−).

a. Which subatomic particle undergoes a change in number in the atom?

b. Is that particle gained or lost? Explain.

c. How is the magnitude of the charge on an ion determined?

EXERCISES

13. Complete the following table:

Isotopic Symbol Z A p+ n0 e-

𝐶612

𝐹𝑒3+2656

𝑆2−1632

42 98 42

50 70 48

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15 16 18

14. Rutherford’s gold foil experiment‖ involves passing a beam of α-particles

(i.e. helium nuclei, 𝐻𝑒2+24 ) through a very thin sheet of gold. Most of the

α -particles pass through the gold foil (a very dense metal) with little or no

deflection. However, a few of the α-particles are observed to be deflected

significantly—some were even deflected back to the source!

a. Explore the PhET Simulation at: https://goo.gl/kb1cy5

Record your observations.

b. Explain why most of the α-particles pass directly through the gold foil with little to no deflection.

c. Explain why only a very small fraction of the α-particles have large deflection angles.

d. Explain why some of the α-particles are deflected back to the source. What does this tell you about the

structure of the atom?

15. What is the net charge on every atom? Explain why.

16. An oxide ion (oxygen ion) has a 2– charge. (Use your periodic table if necessary)

a. How many protons does the oxide ion have?

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b. How many electrons does and oxide ion have?