C1. Atomic Structure

Question 1

What do compounds contain?

Answer 1

More than one element

Question 2

What is the structure of an atom?

Answer 2

Tiny nucleus in the centre and electrons surrounding it

Question 3

What do chemical equations show?

Answer 3

The reactants and products in a reaction, these should always be balanced

Question 4

What is the law of conservation of mass?

Answer 4

No atoms are lost or made during a chemical reaction, so mass of products equals mass of reactants.

Question 5

Why does the law of conservation of mass sometimes seem to be broken?

Answer 5

When gases are reactants or products. For example gas may escape into the air or substance increases in mass when heated in air this is because oxygen gas from air is a reactant

Question 6

What is a mixture?

Answer 6

Made up of two or more substances that are not chemically combined

Question 7

How can a mixture be separated?

Answer 7

• a physical process (no new substances are made as its not a chemical reaction)
• filtration ~ separate insoluble in a solvent from soluble in a solvent
• crystallisation ~ separate a soluble solid from a solvent
• distillation ~ separate a solvent from soluble solids dissolved in solvent
• fractional distillation ~ separate miscible liquids (have different boiling points)

Question 8

Dalton:

Answer 8

• early 1800s
• linked his ideas to strong experimental evidence
• suggested atoms were tiny, hard spheres which could not be divided

Question 9

Thompson:

Answer 9

• end of 1800s
• discovered tiny negative particles called electrons
• “plum pudding” model
  
  • negative electrons were embedded in a ball of positive charged

Question 10

Geiger and marsden:

Answer 10

• experimented with alpha particles by firing them at very thin gold foil
• few of them repelled showing that there must be a tiny spot of positive charge in centre of atom

Question 11

Rutherford:

Answer 11

• proposed nuclear model based on Geiger and marsden

- electrons orbit around nucleus which contains protons

Question 12

Bohr:

Answer 12

• suggested that electrons were orbiting nucleus in energy levels (shells)
• electrons were set distance from nucleus
• bohrs theoretical calculations matched the experimental observations

Question 13

Chadwick:

Answer 13

• 1932

- provided experimental evidence that showed the existence of uncharged particles called neutrons in the nucleus

Question 14

Atomic number =

Answer 14

Number of protons which is the same number of electrons

Question 15

Mass number =

Answer 15

Number of protons + neutrons

Question 16

What is an ion?

Answer 16

Charged atom

Question 17

If an atom gains electrons it is?

Answer 17

Negative ion

Question 18

If an atom loses electrons it is?

Answer 18

Positive ion

Question 19

What is an isotope?

Answer 19

Atoms of the same element with different numbers of neutrons. They have the same chemical properties but not physical