Atoms

Question 1

define - atom

Answer 1

basic building blocks of matter

Question 2

define - nucleus

Answer 2

organelle inside cell - contains DNA

Question 3

electon shells

Answer 3

outside part of an atom around the atomic nucleus

Question 4

atomic number

Answer 4

number of protons an atom has

Question 5

Protons - charge and location in atom

Answer 5

positive charge
located in nucleus

Question 5

mass number

Answer 5

number of protons + neutrons

Question 6

describe structure of an atom

Answer 6

• Each atom is made up of smaller particles - electrons,protons & neutrons (subatomic particles).
• the center of the atom is the nucleus.
• Nucleus constraints protons and neutrons.

Question 7

neutrons - charge and location in atom

Answer 7

neutral charge
located in nuclues

Question 8

electrons - charge and location in atom

Answer 8

negative charge
located outside the nucleus in the electron shells

Question 9

what is meant by a neutral atom

Answer 9

number of protons is equal to number of electrons

atom in neutral

Question 10

Electron shells and arrangement

Answer 10

• electrons are arranged in shells (energy levels)
• the levels CLOSEST to the nucleus are of LESS energy
• Electron cloud model (or wave model)
• spherical cloud of varying density
• varying dentistry shows where an electron is more or less likely to be

Question 11

Maximum number of electrons in each shell.

Answer 11

2,8,8,2 ( first 20 elements)
RULE : 2n^2 - (n = shell number)

Question 12

Relate the number of valence electrons to the group number on the periodic table

Answer 12

periods (horizontal) = number of shells that contain electrons

groups (vertical) = number of electrons in valence shell.
- for groups 13-18, subtract 10

Question 13

Flame tests and the colours of metal ion

Answer 13

• heating an element can cause an electron to absorb energy & jump to a higher energy level or shell

electron is excited & unstable & quickly returns to a lower energy level, releasing a fixed amount of energy which may be in the form of coloured light

VISIBLE LIGHT can be emitted when electrons return to a lower energy level.

Question 14

Explain why the outer shell (valence shell) electrons are important

Answer 14

valence shells are important because they determine an atom’s chemical properties & ability to bond with other atoms.

Question 15

ion

Answer 15

an atom that carries positive or negative electric charge as a result of having lost or gained electron/s.

Question 15

cation

Answer 15

a positively charged ion formed by losing electrons

Question 16

Why do atoms form ions?

Answer 16

atoms form ions to achieve a stable electron configuration. by gaining or losing electrons to attain a full outer shell.

Question 16

anion

Answer 16

a negatively charged ion formed by gaining electrons

Question 17

which type of element form anions

Answer 17

non-metals

Question 17

which type of metals form ions

Answer 17

metals

Question 18

Explain the difference between cations and anions.

Answer 18

Cations are positively charged ions formed by losing electrons
anions are negatively charged ions formed by gaining electrons.

Question 19

Explain how bonds form between ions

Answer 19

when a metal cation and a non-metal anion react together in a chemical reaction an ionic bond is formed.

Question 20

List the experimental observations indicating that a chemical reaction has occurred

Answer 20

COBALT
C- colour changed
O-odor change
B-bubbles appearing
A- Appearance or disappearance of a solid
L-Light or sound produced
T- Temperature change

Question 20

What are the reactants of a chemical reaction?

Answer 20

the subatances you have at the beginning are called reactants.

Question 21

What are the products of a chemical reaction?

Answer 21

when the reaction is complete, you have new substances which are called the products.

Question 22

Describe the difference between a physical and a chemical change.

Answer 22

• a physical change involves change in physical state or appearance without altering its chemical composition. (shape,size)

chemical change involves the formation of new substances with different chemical properties.

Question 23

List the factors that can increase the rate of a chemical reaction

Answer 23

anything that increases the number of successful collisions between reactant particles will speed up a reaction

• increased temperature
• increased concentration of dissolved reactants
• increased surface area of solid reactants
• use of a catalyst.

Question 23

Explain the meaning of ‘rate of a chemical reaction’

Answer 23

The rate is a measure of how fast the products are made or reactants are used up.
The speed of a reaction is called the rate of the reaction.

Question 24

Explain how these factors increase the reaction rate

higher temp

Answer 24

• At a higher temperature, particles have more energy. This means they move faster and are more likely to collide with other particles.
• When the particles collide, they do so with more energy, and so the number of successful collisions increases.

Question 25

Explain how these factors increase the reaction rate
- catalyst

Answer 25

a catalyst speeds up a chemical reaction. a catalyst provides a surface for the reactions to take place on and hence increases the frequency of collins.
It also provides a different pathway for the ration with lower energy required.

Question 25

Explain how these factors increase the reaction rate

higher concentration

Answer 25

at a higher concentration there are more particles in the same amount of space. This means that the particles are more likely to collide and therefore more likely to react.

Question 26

explain the function of a catlayst

Answer 26

A catalyst speeds up chemical reactions by lowering the energy needed to start them, making reactions happen faster. It does this without being used up itself.