Unit 1: 2.4: Subatomic Particles, Isotopes, and Ions

Question 1

Protons, neutrons, and electrons.

Answer 1

subatomic particles

Question 2

Neither positively nor negatively charged.

Answer 2

neutral

Question 3

The number of protons in the nucleus of each atom of an element that determines its identity.

Answer 3

atomic number, Z

Question 4

The whole number that is shown above the element symbol on the periodic table.

Answer 4

atomic number, Z

Question 5

A form of an element whose atoms have the same number of protons but different numbers of neutrons.

Answer 5

isotopes

Question 6

The sum of the number of protons and the number of neutrons in an atom; the distinguishing difference among isotopes of a given element. It is abbreviated as A.

Answer 6

mass number

Question 7

An atom or group of atoms that has gained or lost electrons and therefore has a net negative or positive charge.

Answer 7

ions

Question 8

A positively charged ion.

Answer 8

cation

Question 9

A negatively charged ion.

Answer 9

anion

Question 10

How many protons, neutrons, and electrons are in a neutral atom of the following isotope:
S-32

Answer 10

Sulfur has an atomic number of 16, so it has 16 protons in the nucleus. The mass number of this isotope is given as 32, so the number of neutrons in the nucleus is n = A-Z-32-16 16. A neutral atom always has the same number of electrons as protons, so an atom of S-32 contains 16 protons, 16 neutrons, and 16 electrons.

Question 11

How many protons, neutrons, and electrons are in a neutral atom of the following isotope:
^19 F

Answer 11

Fluorine has Z = 9, so it has 9 protons in its nucleus. Since it is a neutral atom, it must have an equal number of electrons. The mass number of this isotope is 19, so the number of neutrons in the nucleus is equal to n=A-Z19-910. Therefore, an atom of F-19 contains 9 protons, 10 neutrons, and 9 electrons.

Question 12

How many protons, neutrons, and electrons are in a neutral atom of the following isotope:
A neon atom with equal numbers of protons and neutrons in the nucleus.

Answer 12

Neon is atomic number 10, so this neon atom has 10 protons in the nucleus and 10 electrons. Since the number of neutrons in this case is equal to the number of protons, this isotope has 10 neutrons in its nucleus, too

Question 13

How many protons, neutrons, and electrons are in a neutral atom of the following isotope:
^238 U

Answer 13

Uranium has Z92, which is indicated in this notation by the subscript on the left. The mass number of this isotope is 238, so the number of neutrons in the nucleus is equal to n = A-Z-238-92146. Since it is a neutral atom, it must have 92 electrons to balance the charge of the 92 protons. Altogether, this atom has 92 protons, 146 neutrons, and 92 electrons.

Question 14

Write the symbols for the following isotope by using an elemental symbol with a superscript:
a helium atom with a mass number of 3

Answer 14

^3 He (The mass number is 3)

Question 15

Write the symbols for the following isotope by using an elemental symbol with a superscript:
An oxygen atom with 7 neutrons in the nucleus

Answer 15

^15 O (oxygen has 8 protons, and this isotope has 7 neutrons, so A=15)

Question 16

Write the symbols for the following isotope by using an elemental symbol with a superscript:
A boron atom with equal numbers of protons and neutrons in the nucleus

Answer 16

^10 B (Boron has 5 protons and the same number of neutrons, so A=10)

Question 17

Write the symbols for the following isotope by using an elemental symbol with a superscript:
A carbon atom that has one more neutron than protons in its nucleus

Answer 17

^13 C (Carbon has 6 protons and, in this isotope, 6+1=7 neutrons. So, A=6+7=13)

Question 18

Assuming the element symbols are correct, is the following isotopic symbol correct? Explain why

Answer 18

Incorrect. Carbon has an atomic number of 6, not 14. Carbon can have a mass of 14, though, so the atomic and mass numbers must have been switched. If the atomic number were correct, making this an isotope of silicon, Si (Z=14), it would still be incorrect because it is impossible for an atom to have a mass number that is less than its atomic number.

Question 19

Assuming the element symbols are correct, is the following isotopic symbol correct? Explain why
O-17

Answer 19

O-17 is correct. This is an isotope of oxygen (Z=8) that has 8 protons and 9 neutrons.

Question 20

Assuming the element symbols are correct, is the following isotopic symbol correct? Explain why

Answer 20

Incorrect. Hydrogen (Z=1) has 1 proton, not 2. Hydrogen have a mass number of 2, however, so the “2” should be a subscript instead.

Question 21

Assuming the element symbols are correct, is the following isotopic symbol correct? Explain why

Answer 21

Incorrect. The atomic number given as a subscript does not match the element symbol. Assuming the element symbol is correct, this notation should be flipped.

Question 22

Assuming the element symbols are correct, is the following isotopic symbol correct? Explain why
S-6

Answer 22

Incorrect. Sulfur has an atomic number of 16, so a mass number of 6 is impossible, The mass number can never be less than the atomic number.

Question 23

Write the isotopic symbol that correctly represents the following:
a hydrogen isotope with 2 neutrons

Answer 23

Question 24

Write the isotopic symbol that correctly represents the following:
An iodine isotope with 78 neutrons

Answer 24

Question 25

Write the isotopic symbol that correctly represents the following:
A polonium isotope with 42 more neutrons than protons

Answer 25

Question 26

Two atoms have 17 protons each, but the first atom contains 18 neutrons, whereas the second contains 20 neutrons. Show that their atomic numbers are the same but that their mass numbers differ.

Answer 26

The atomic number, Z, is the number of protons in an atom. Both of these atoms have 17 protons, so both are the same element, chlorine. To determine the mass numbers, A, of these atoms, add the number of protons and the number of neutrons. For the first atom, A=17+18=35; for the second atom, A=17+20=37. The atoms have the same atomic number but different mass numbers, so they are isotopes of each other, ^35Cl and ^37Cl

Question 27

Two atoms have A=119, but one has 69 neutrons and the other has 70 neutrons. Are they isotopes of each other. If not, what elements do they represent?

Answer 27

A=p+n=Z, so Z=A-n.
For the first atom, Z=119-69=50, which corresponds to the element tin, Sn.
For the second atom, Z=119-70=49, which corresponds to the element indium, In.
As a result, these two atoms are not isotopes of the same element.

Question 28

How many protons and electrons are in the following ion:
F^-

Answer 28

9 protons and 10 electrons

Question 29

How many protons and electrons are in the following ion:
Mg^2+

Answer 29

12 protons and 10 electrons

Question 30

How many protons and electrons are in the following ion:
N^3-

Answer 30

7 protons and 10 electrons

Question 31

How many protons and electrons are in the following ion:
W^6+

Answer 31

74 protons and 68 electrons

Question 32

Write the symbol for the following isotope by using an elemental symbol with a superscript and the charge, if appropriate. Then determine the number of protons, neutrons, and electrons.
A hydrogen atom with a mass number of 3

Answer 32

^3H has 1 proton, 2 neutrons, and 1 electron

Question 33

Write the symbol for the following isotope by using an elemental symbol with a superscript and the charge, if appropriate. Then determine the number of protons, neutrons, and electrons.
An oxygen ion with 7 neutrons and a charge of -2

Answer 33

^15 O ^2- has 8 protons, 7 neutrons, and 10 electrons.
There are two more electrons than there are protons because the anion has a charge of -2.

Question 34

Write the symbol for the following isotope by using an elemental symbol with a superscript and the charge, if appropriate. Then determine the number of protons, neutrons, and electrons.
A selenium ion with a mass number of 78 and a charge of -2

Answer 34

^78 Se ^2- has 34 protons, 78-34=44 neutrons, and 36 electrons. There are two more electrons than there are protons because the anion has a charge of -2.

Question 35

Write the symbol for the following isotope by using an elemental symbol with a superscript and the charge, if appropriate. Then determine the number of protons, neutrons, and electrons.
A manganese ion with 30 neutrons and a charge of +4

Answer 35

^55 Mn ^4+ has 25 protons, 30 neutrons, and 21 electrons. There are four fewer electrons than there are protons because the cation has a charge of +4.