History and Structure of the Atoms

What are Dalton’s 5 postulates about atoms?

1. All matter is made of tiny, indivisible particles called atoms. 2. Atoms of a given element are identical in mass and properties; atoms of different elements are different in mass and properties. 3. Atoms cannot be created or destroyed. 4. Atoms of different elements combine in simple whole-number ratios to form chemical compounds. 5. In chemical reactions, atoms are combined, separated, or rearranged.

What are the three subatomic particles that make up atoms?

Protons, neutrons, and electrons.

What subatomic particle did J.J. Thomson discover in 1897?

The electron.

What was the name of Thomson’s model of the atom (what did it look like)?

The "plum pudding model", where negatively charged electrons were embedded in a positively charged sphere, much like plums in a pudding.

Which subatomic particle has a charge of -1?

The electron.

What subatomic particle did Ernest Rutherford discover in 1911?

The proton.

In addition to discovering a subatomic particle, what else did Ernest Rutherford discover about atoms?

He discovered the atomic nucleus, a dense, positively charged center where most of the atom's mass is concentrated. He also concluded that atoms are mostly empty space.

What subatomic particle did James Chadwick discover?

The neutron.

What is the mass of a proton?

Approximately 1 \text{ amu} (1.672 \times 10^{-27} \text{ kg}).

What is the mass of a neutron?

Approximately 1 \text{ amu} (1.674 \times 10^{-27} \text{ kg}), which is slightly greater than a proton.

What is the mass of an electron?

Approximately 0 \text{ amu} (9.109 \times 10^{-31} \text{ kg}), which is significantly smaller than protons or neutrons.

What are the charges of all three subatomic particles?

Proton: +1, Electron: -1, Neutron: 0 (neutral).

How do you determine the mass number of an atom?

By adding the number of protons and neutrons in the nucleus (\text{Mass Number} = \text{Protons} + \text{Neutrons}).

Which subatomic particle determines the identity of an atom?

The proton (the atomic number, which is determined by the number of protons, defines the element).

Which subatomic particle determines the stability of an atom?

The neutron (specifically, the neutron-to-proton ratio influences nuclear stability).

Which subatomic particle determines the reactivity of an atom?

The electron (specifically, the valence electrons in the outermost shell).

What is the definition of an isotope?

Atoms of the same element that have the same number of protons but different numbers of neutrons, resulting in different mass numbers.