The Atom: Basic Building Block Of Matter: Models Of Matter

Question 1

Democritus theory

Answer 1

• Suggested the matter was made up of small basic particles
• Called them atoms
• Shut down for 2000 years until someone else came up with atomic theory

Question 2

Daltons model

Answer 2

•18th century
•Knew elements combined in fixed ratios e.g H and O combine in a mass ratio of 1:8
•Assumptions made by dalton:
-Matter is made up of indestructible and invisible atoms
-atoms of same element are identical
-atoms of diff. elements differ from one another

•No reference to the electrical nature of matter

Question 3

Thomsons model

Answer 3

•Worked with cathode ray tubes
•Discovered cathode rays were a stream of negatively charged particles called electrons
•Found out:
-electrons are identical
-substances differ due to the amount of electrons and their arrangement
•Model is a solid sphere with positive and negative particles evenly distributed throughout to make the atom neutral
•After experiment with Milikan the found that an electron is about 2000 times less than the mass of a proton

Question 4

Rutherfords model

Answer 4

• Perfect one of the most significant experiments in science
• Used alpha particles(positively charged particles given off by radioactive substances) to bombard gold foil
• Realised electrons are very small therefore would have little effect on alpha particles

Question 5

Aim of rutherford model

Answer 5

Locate protons location in atoms.

Question 6

Chadwick

Answer 6

• Couldn’t explain why helium which is four times bigger than hydrogen and not twice as large.
• 1932, he bombarded beryllium with alpha particles
• Found neutral particles and called them neutrons

Question 7

What are the fixed orbits around the nucleus

Answer 7

Energy levels

Question 8

Atomic number

Answer 8

Number of protons in an atom

Question 9

Atomic mass

Answer 9

Protons plus neutrons

Question 10

Isotopes

Answer 10

Atoms of the same element which have different mass numbers

•Have same amount of protons in nucleus but different number of neutrons

Question 11

What really are the relative atomic masses

Answer 11

Average values of the different isotopes

Question 12

What is positively charged ion

Answer 12

Cation

Question 13

What is a negatively charge ion

Answer 13

Anion

Question 14

How does an atom become a cation

Answer 14

It gives up electrons

Question 15

When does an atom become a anion?

Answer 15

When it gains an electron

Question 16

What ions receive -ide

Answer 16

Negative ions

Question 17

What assumptions did Bohr make?

Answer 17

• Electrons only move in fixed permitted orbits
• That electrons in the fixed orbitals have definite energy which can’t change while the electron is moving in its orbital

Question 18

What are fixed energies called?

Answer 18

Energy levels

Question 19

What do electrons need to do to radiate energy?

Answer 19

Has to fall from a higher energy level to a lower energy level

Question 20

What happens when an electron absorbs energy?

Answer 20

It jumps to higher energy levels

Question 21

Orbital?

Answer 21

A region in space where the probability of finding an electron is greatest

Question 22

S- orbital

Answer 22

Spherical in shape
•Symmetrical but differ in size
•Only one in each energy level

Question 23

P- orbitals

Answer 23

•Occur in groups of three at right an