mass #

atomic #

protons +

neutrons=

protons=

Atomic Symbols

Element AtomicNumber

Protons Neutrons Electrons

19 19 20

S 17

39Ca

14 6

K 19 1939

16 16 161633

20 20 19 2020

66 86 C

Elements are identified by atomic number (protons).

11H

21H

31H

protium deuterium tritium

element:mass:

_________:

same or differentsame or different

same # of protons & electrons,

BUT different # of neutrons

Isotopes

1. The number of protons in the nucleus is…

A. the mass number.

B. the atomic number.

C. the same as the number of neutrons.

D. the total of protons and neutrons.

Quick (but challenging) Quiz!

2. The mass number is…

A. the number of protons.

B. the number of neutrons.

C. the total of protons and electrons.

D. the total of protons and neutrons.

Quick (but challenging) Quiz.

3. Isotopes of an element have…

A. the same mass number.

B. different atomic numbers.

C. the same number of protons but different mass numbers.

D. the same number of protons but different numbers of neutrons.

Quick (but challenging) Quiz.

4. How many neutrons are in an atom of potassium–40 ? (40K)

(Atomic Number = 19)

A. 19 neutrons

B. 21 neutrons

C. 40 neutrons

D. 59 neutrons

Quick (but challenging) Quiz.