chemistry in science

Atom

The basic building block of all matter

Element

A pure substance made up of only one type of atom

Compound

A substance, made up of two or more different elements (atoms) bonded together in a fixed ratio

Elements in the same period have the same

number of electron shells

Elements in the same group have the same

Number of valence electrons

What is the mass number of an element

The total number of protons and neutrons an atom has 

What is the atomic number of an element

The number of protons an atom has.  

What is the Bohr model of the atom

Describes electrons as being physical particles, moving on one path in one direction

What is unique about elements in Group 18

All have full valence shells 

List 3 properties of Alkali metals

reactive, soft, low melting + boiling points

List 3 properties of Halogens 

reactive, toxic, brittle when solid

Properties of metals

malleable, shiny (lustrous), high melting and boiling point, good conducters of electricity and heat, solids, ductile.

Properties of non-metals

dull, low melting and boiling point, bad conductors of electricity and heat, brittle

examples of metalloids

boron, silicon, germanium.

What is the mass of an electron

1/1837

group 1 (not hydrogen)

alkali metals

group 2

alkaline earth metals

group 3-12

transition metals

group 17

halogens

group 18

noble gases

What is the first row called

Lanthanides

What is the second row called

Actinides

properties of noble gases

non-flammable, full valence shell, unreactive, colourless, tasteless

neutrons charge, symbol and location in atom

0, N, nucleus

protons charge, symbol and location in atom

+1, P, nucleus

electrons charge, symbol, and location in atom

-1, e, outside the nucleus

When are protons and electrons not equal

When an atom is not neutral (ions)

The periodic table is arranged in order of

increasing atomic number

columns of periodic table

groups

rows of periodic table

periods

Isotopes

atoms of the same element with different mass number

What are the 2 types of ions? Describe each.

Ions are formed by the gain /loss of electrons

Cations is formed by the loss of electrons. Metals form cations

Anion is formed by the gain of electrons. No metals form anions

How is an ionic bond formed?

Ionic bond is formed by the transfer of electrons between a metal and non metal. Metals lose electrons to form cations, non metals gain electrons to form anions. Due to strong electrostatic force of attraction between the ions, ionic bond is formed.

Isomer

Isomer is a compound that has the same molecular formula but different structural formulas

Metallic bond

Metallic bond is formed due to strong electrostatic force of attraction between positive metal ions and delocalised electrons 

Covalent Bond:

Covalent bond is formed due to sharing of valence shell electrons between  non -metals.

What is rate of a reaction?

The rate of a reaction is how quickly reactants are converted into products.

Factors that affect rate of a reaction

1.Concentration 

2. Temperature 

3. Pressure 

4. Surface area 

5. Catalysts/enzymes 

6. Agitation (stirring) 

Explain why the rate of reaction increases with the increase in surface area ? 

Rate of reaction increases with the increase in surface area because increasing the surface area causes the frequency of successful collisions to increase. Higher the surface area higher the rate of a reaction. 

Explain why the rate of reaction increases with the increase in temperature? 

With the increase in temperature, rate of a reaction increases due to : 

 

• the particles have more (Kinetic energy) energy and will collide with greater force 

• the frequency of collisions will increase, increasing the rate of a reaction 

Explain what a catalyst is and give an example of a catalyst. 

A catalyst is a substance that increases the rate of a chemical reaction without being used up.  

 

Catalysts enables/helps the reaction to occur at a lower temperature.  

Example: Catalytic convertors(containing Platinum) in the car converts toxic carbon monoxide into carbon dioxide 

Explain how enzymes are a type of a catalyst .

Enzymes are biological catalysts. They are proteins that help speed up chemical reactions in the body e.g. digestive enzymes 

What is activation energy ? 

Activation energy is the energy required to start a reaction.