Question

quiz 5 unit 3 atoms and subatomic particles

1. what greek philosopher was the first person to propose the idea that matter is made of tiny individual particles called atoms?

a) democritus
c) dalton
b) bohr
d) rutherford

1. how many protons are in the nucleus of an atom of beryllium?

a) 9
b) 2
c) 5
d) 4

1. what is the mass number of an atom that contains 19 protons, 19 electrons, and 20 neutrons?

a) 39
b) 20
c) 19
d) 58

Explanation:

1. Democritus was the Greek philosopher who first proposed the idea of atoms. Bohr proposed the Bohr model of the atom. Dalton proposed Dalton's atomic theory. Rutherford proposed the nuclear model of the atom.
2. The atomic number of beryllium is 4. The number of protons in an atom is equal to its atomic number.
3. The mass number of an atom is the sum of the number of protons and neutrons. So, mass number = 19 (protons) + 20 (neutrons) = 39.

Answer:

1. A. Democritus
2. D. 4
3. A. 39