Dr. Esker Chapter three

What are atoms?

Atoms are extremely small particles that are indivisible and indestructible, compose elements.

Dalton proposed that atoms of a given element are identical in size, mass, and chemical properties, and different from those of other elements.

What is the significance of Dalton's atomic theory?

Different atoms combine in simple whole-number ratios to form compounds.

What does Dalton's theory say about how atoms combine?

What happens to atoms during a chemical reaction?

Atoms are separated, combined, or rearranged.

What was J.J. Thomson's contribution to atomic theory?

Thomson measured the charge-to-mass ratio of a charged particle and proposed the plum pudding model of the atom.

What does the plum pudding model suggest?

It suggests that the atom is a uniform, positively charged sphere containing electrons.

What did Robert Millikan determine using the oil-drop apparatus?

Millikan determined the charge of an electron.

What was Ernest Rutherford's key experiment?

Rutherford aimed alpha particles at a thin sheet of gold foil to study their interaction with matter, leading to the discovery of the nucleus.

What did Rutherford discover about the nucleus?

He found that the nucleus contains positively charged particles called protons.

What did James Chadwick discover?

Chadwick discovered neutrons, neutral particles in the nucleus that account for the remainder of an atom's mass.

What is the atomic number?

The atomic number is the number of protons in the nucleus of an atom, which is equal to the number of electrons in a neutral atom.

How is atomic mass calculated?

Atomic mass is the sum of the number of protons and neutrons in an atom.

How do you calculate the number of neutrons in an atom?

Neutrons can be calculated by subtracting the atomic number from the atomic mass.

What did Henry Moseley discover?

Moseley experimentally discovered the atomic number, which is the number of protons in the nucleus.