Question

unit 3a: the atom and the nucleus study guide

1. fill in the following chart

subatomic particle	mass	charge	location
neutron		no charge
electron		neg charge

1. if i know the atomic number of an element, i know its number of what subatomic particle?

protons

1. where is most of the mass of an atom located?
2. in a neutral atom, what two subatomic particles are in equal amounts?
3. given the following isotopic notation, answer the questions below

a. what element is this?
copper
b. what is its atomic mass?
63
c. what is its atomic number?
29
d. how many protons does it have?
29
e. how many neutrons?
34
f. how many electrons?
29

1. given the following isotopic notation, answer the questions below uranium - 235

a. what element is this?
uranium
b. what is its atomic mass?
235
c. what is its atomic number?
92
d. how many protons does it have?
92
e. how many neutrons?
143
f. how many electrons (assume the atom is neutral)?
92

1. if an element has a charge of +3, how many protons and electrons does it have? atomic number = 12
2. if an element has a charge of -4, how many protons and electrons does it have? atomic number = 47

Explanation:

Step1: Recall sub - atomic particle properties

Protons have a positive charge, neutrons are neutral, and electrons are negative. Protons and neutrons are in the nucleus, electrons are in the electron - cloud.

Step2: Understand atomic number relationship

The atomic number is equal to the number of protons.

Step3: Locate atomic mass

The mass of an atom is mainly in the nucleus (protons + neutrons).

Step4: Analyze neutral atom

In a neutral atom, the number of positive protons equals the number of negative electrons.

Step5: Interpret isotopic notation

For $_{29}^{63}Cu$, the bottom number is the atomic number (number of protons), the top number is the atomic mass. Neutrons = Atomic mass - Atomic number. In a neutral atom, electrons = protons.

Step6: Apply to uranium - 235

Similar to step 5, for uranium - 235, use the atomic number and atomic mass relationships.

Step7: Calculate for charged atom (+3 charge)

Given atomic number = 12 (protons = 12), and charge = +3, so electrons = protons - charge.

Step8: Calculate for charged atom (-4 charge)

Given atomic number = 47 (protons = 47), and charge=-4, so electrons = protons+|charge|.

Answer:

1.

Subatomic Particle	Mass	Charge	Location
Neutron	1 amu (approx.)	None (0)	Nucleus
Electron	$\frac{1}{1836}$ amu (approx.)	Negative (-1)	Electron - cloud outside nucleus

1. Protons
2. Nucleus
3. Protons and electrons

5.
a. Copper
b. 63
c. 29
d. 29
e. 34 (Calculation: $63 - 29=34$)
f. 29
6.
a. Uranium
b. 235
c. 92
d. 92
e. 143 (Calculation: $235 - 92 = 143$)
f. 92

1. Protons: 12, Electrons: 9 (Calculation: Atomic number = number of protons = 12. Charge = +3, so number of electrons = $12-3 = 9$)
2. Protons: 47, Electrons: 51 (Calculation: Atomic number = number of protons = 47. Charge=-4, so number of electrons = $47 + 4=51$)