Science mid year exam | Secondary 4

Thomson atom model

Rutherford atom model

Bohr-Rutherford atom model

Simplified Atomic atom model

Groups

Represents valence electrons

Period

Number of rings on atom

Staircase

Metals are left, metalloids are alongst it, non-metals on right

Metal

good conductors, shiny, they are malleable

Non-metal

not shiny, poor conductors

Metalloids

Properties of metals and non-metals

Alkali Metal

Most reactive, reactive with are, always combined with other elements

Alkali Earth Metals

Excellent conductors, melting point higher than 1st group, 2nd most reactive

Halogens

Form salt when combined with alkali metals, form strong acid when combined with hydrogen, always combined with something

Noble gases

lack of reactivity, doesn’t combine with other element

Ionization/Ions

When a neutral atom or molecule becomes charged by either losing one or more electrons

Which properties lose electrons

Metals

Which properties gains electrons

Non-metals

Atomic radius

Size of a neutral atom

How do we measure the atomic radius of an atome

Increases down each group & decreases across each period

Where in the periodic table are the elements with a higher melting point& better conductivity

The middle

Isotopes

Different types of the same element. Because of different amounts of neutrons

Why do atoms bond

To be in a stable state

Octet rule

Elements gaining or losing electrons to be in a stable state

Positive Ions

lose electrons

Negative Ions

Gain electrons

Ionic bond

Metals + Non-metals

In Ionic bonds, what do the molecules end with

Ide

Covalent bond

Non-metal + Non-metal

What does a Ionic bond do

Give electrons

What does a covalent bond do

Share electrons

Diatomic elements

Covalent bonds when the same elements bond

Electric conductivity

The ability of electric currents to flow through a solution

Types of electrolytes

Acids, bases, and salts

Acids

“H” in the front of the formula, turns litmus paper red

Bases

“OH” in the end of the formula, turns litmus paper blue

Salts

Metals + Non-Metals, Doesn’t have “H” or “OH”

Electrolytes

Substance when dissolved in water allows electric currents to flow through it

Non-electrolytes

Non-metals + no-metals (not acids)

Physical change

It doesn’t modify the nature or characteristic properties of matter

What are some physical changes

crushing, cutting, bending

Chemical change

It modifies the nature and characteristic properties of matter

What are some chemical changes

formation of gas, precipitation, change in colour, heat and light

Combustion

A form of oxidation that releases a large amount of energy

Celullar Resporation

When glucose and oxygen make carbon dioxide and water

Photosynthesis

Solar energy, carbon dioxide and water make glucose and oxygen

Nuclear stability

Atomic nucleus to resist radioactive decay and maintain

What does the stability of a nucleus depend on

Its size and the number of neutrons it contains

Radioactivity

Unstable atoms spontaneously transforms into a more stable atom, or several more, while releasing energy

Nuclear Fission

Nuclear reaction when the nuclease of a large atom splits into one or more smaller nuclei

Nuclear Fusion

Two or more smaller nuclei join together to form a heavier nucleus

Electricity

Phenomena caused by positive and negative charges

Electric charge

Electrons are negatively charged while protons are positively charged. A negative and positive attract & two negatives/positive repel

Insulation

Prevents electric current to flow

Conduction

Transmits electric current from one part to another

Series circuits

The circuit is connected with one direction

Parallel

The circuit has multiple branches

Magnetism

It’s the property that make some things attract and repel

Law of conservation

Energy can’t be created nor destroyed. It always remains constant

Heat

the transfer of energy(change in temperature)

Temperature

How hot or cold the particle are

Endothermic

Takes energy

Exothermic

Loses energy