The Atom

Question 1

Atom definition?

Answer 1

Smallest part of an elements which retains the characteristics of that element.

Question 2

When did the idea of atoms become a scientific theory?

Answer 2

1808

Question 3

Dalton’s atomic theory?

Answer 3

1) all matter is made up of atoms
2) all atoms of an element are similar to each other
3) atoms of different elements can combine to form compounds
4) atoms cannot be created or destroyed in chemical reactions

Question 4

What kind of microscope can be used to see atoms?

Answer 4

Scanning tunnelling microscope

Question 5

Who discovered the electron and when?

Answer 5

Thomson in 1897

Question 6

How was the electron discover?

Answer 6

Thomson applied electricity to a glass tube producing cathode rays. The rays were attracted to a positively charged electrode meaning the rays must be negatively charged.

Question 7

Who proposed the plum pudding model?

Answer 7

Thomson

Question 8

Explain the plum pudding model?

Answer 8

A random distribution of electrons within a positive cloud.

Question 9

Who disproved the plum pudding model and when?

Answer 9

Rutherford 1911

Question 10

How did Rutherford discover the nucleus?

Answer 10

By aiming positively charged particles at a thin sheet of gold. Results showed most carried on straight but occasionally some were deflected meaning atoms must have a small positive centre (nucleus)

Question 11

Mass and charge of an electron?

Answer 11

1/2000 -1

Question 12

Mass and charge of a proton

Answer 12

1 +1

Question 13

Mass and charge of a neutron?

Answer 13

1 0

Question 14

Atomic mass unit (AMU) definition?

Answer 14

One-twelfth of the mass of carbon 12

Question 15

What is the atomic number?

Answer 15

The number of protons (also number of electrons in a neutral atom)

Question 16

What is the mass number?

Answer 16

The number of protons and neutrons

Question 17

What is an isotope?

Answer 17

An atom of the same element which has a different amount of neutrons

Question 18

Relative atomic mass (Ar) definition?

Answer 18

The weighted mean mass of an atom of an element compared to 1/12th of the mass of an atom of carbon-12 (1 amu)

Question 19

Definition of relative isotopic mass?

Answer 19

The mass of an atom of an isotope compared to 1/12th of the mass of an atom of carbon-12

Question 20

Definition of relative molecular mass (Mr)?

Answer 20

It is the mean mass of a molecule compared to 1/12th of the mass of an atom of carbon-12

Question 21

What does a mass spectrometer determine?

Answer 21

Percentage abundance and isotopic mass of each isotope

Question 22

What is needed to calculate relative atomic mass (Ar)?

Answer 22

Percentage abundance and isotopic mass of each isotope
E.g. Mg-24 at 79% Mg-25 at 10% and Mg-26 at 11%
(24x79)+(25x10)+(26x11)
————————————
100

Question 23

How to work out Relative molecular mass (Mr)?

Answer 23

Add together all the relative atomic masses of the atoms in the molecule