Atoms

Question 1

The number of protons in an atom is called the _________________.

Answer 1

atomic number

Question 2

Which subatomic particle contributes charge but no significant mass to an atom?

Answer 2

electron

Question 3

The number of _______________ is a unique characteristic of an element.

Answer 3

protons

Question 4

The nucleus of an atom __________.

Answer 4

contains protons and is positively charged

Question 5

In an atom, the number of __________ and __________ are always equal.

Answer 5

electrons and protons

Question 6

All plutonium atoms have the same number of __________, while the number of __________ may vary for different atoms of plutonium.

Answer 6

protons and neutrons

Question 7

Which pair of atoms is a pair of isotopes?

10 11
B and B
5 5

45 44
Sc and Ca
21 20

11 11
Na and Na
22 23

16 17
S and Cl
34 37

Answer 7

10 11
B and B
5 5

Question 8

Determine the atomic number, mass number, and numbers of each subatomic particle in an atom of uranium-238 (238U). Also indicate the average atomic mass for all atoms of the element.

Answer 8

atomic number:
92

mass number:
238

protons:
92

neutrons:
146

electrons:
92

average atomic mass, with abbreviated units:
238.0 amu

Question 9

Determine the atomic number, mass number, and symbol of an atom that contains 30 protons and 35 neutrons. Also indicate the average atomic mass for all atoms of the element.

Answer 9

atomic number:
30

mass number:
65

symbol (element abbreviation; letters only):
Zn

average atomic mass, with abbreviated units:
65.38 amu

Question 10

Determine the number of valence electrons in an atom of each element below, and draw the atom’s Lewis symbol in your notes.

Answer 10

a) beryllium:
2 valence electrons

b) lead:
4 valence electrons

c) sulfur:
6 valence electrons

Question 11

H2SO4

H atoms:

S atoms:

O atoms:

Answer 11

H2SO4

H atoms:
2

S atoms:
1

O atoms:
4

Question 12

Mg3(PO4)2

Mg atoms:

P atoms:

O atoms:

Answer 12

Mg3(PO4)2

Mg atoms:
3

P atoms:
2

O atoms:
8

Question 13

(NH4)4Ce(SO4)4

N atoms:

H atoms:

Ce atoms:

S atoms:

O atoms:

Answer 13

(NH4)4Ce(SO4)4

N atoms:
4

H atoms:
16

Ce atoms:
1

S atoms:
4

O atoms:
16

Question 14

BPA, which has a chemical formula of (CH3)2C(C6H4OH)2

C atoms:

H atoms:

O atoms:

Answer 14

BPA, which has a chemical formula of (CH3)2C(C6H4OH)2

C atoms:
15

H atoms:
16

O atoms:
2

Question 15

How many subatomic particles does an atom of 89Y contain?

Answer 15

39 protons, 50 neutrons, 39 electrons

Question 16

How many valence electrons are present in an aluminum atom?

Answer 16

3

Question 17

Determine the number of each type of atom in a molecule of Co(NH3)6Cl3.

Co atoms:
1

N atoms:
6

H atoms:
18

Cl atoms:
3

Answer 17

Co atoms:
1

N atoms:
6

H atoms:
18

Cl atoms:
3

Question 18

How many valence electrons are present in a molecule of K2Se?

Answer 18

8