chemistry - revision

Nucleus contains

protons and neutrons

electron shell (outside)

a grouping of electrons surrounding the nucleus of an atom

neutral atom

same number of protons and electrons

mass number

the total number of protons and neutrons in an atom

atomic number

the number of protons in an atom

Isotopes

Versions of the same chemical element. With different numbers of neutrons but the same amount of protons

shell 1 contains

2 electrons

shell 2,3,4 contains

8 electrons

ground state

when an atom is natturally at its lowest state

excited electrons

electrons jump to a higher energy level.when returned to their ground state,their energy is released in light

valence electrons

outermost shell of electrons

Cation

an atom with 1,2,3 valence electrons it will lose electrons to have a full outershell. a posotiv ion is formed

Anion

an atom with 5,6,7 valence electrons it will gain to have a full outershell. a negative ion is formed

Ion

are atoms that have gained or lost one or more electrons.

law of conservation of mass

the total mass of all the reactants is equal to the total mass of the products.

Aqueous soloution

a mixture in which somthing is dissolved in water:water is the solvent

alkali metal

an element in group 1 of the periodic table;alkali metals are highly reactive and explode in water

Precipitation

when two aqueous soloutions are mixed and a solid is formed.

Mass of atom located

the nucleus,protons and nutrons are heaveir then electrons.

exothermic reaction

produces heat when products are formed

endothermic reaction

absorbs heat when the products are formed

Combustion reaction

when an element or compund reacts with oxygen to produce a flame (fire)

Hydrocarbon Combustion

When hydrocarbon undergoes combustion carbon dioxie and water is produced

combination/synthesis reaction

when 2 reactants make 1 product. A+B->AB

decomposition reaction

When 1 ractant makes 2 products (reverse of synthesis) AB->A+B

Single replacemnet reaction

A single replacement reaction involves one element replacing another element in a compound.(No longer joined to anything)Eg. A + BC → AC + B

Double replacmnet

A double replacement reaction involves the reaction of two compounds to form two new compounds. AB + CD → AD + CB

percipitation reaction

It's the same as a double replacement reaction but one of the compounds produced is a solid and the other one a solution. AgNO3 (aq) + NaCl (aq) 🡪 AgCl (s) + NaNO3 (aq)

Neutralisation reaction

Is a reaction where an acid and base react to produce a salt and water. That is after the reaction is over all that remains is salt and water which are neither acidic nor basic.Eg. HCl (aq) + NaOH (aq) 🡪 NaCl (aq) + H2O (l)

collision theory

states that the particles must collide in order for a reaction to proceed.

in order for a reaction to proceed the particles must

be in an orientation favourable for breacking those bonds

rate of reaction

is the speed at which a chemical reaction occurs

increase concentration

The rate of reaction as there are a greater number of particles available to react. Increasing the likelyhood of the particles colliding

increase temprerature

the temperature increases the kinetic energy of particles.

increase surface area

Breaking it into smaller pieces increases the surface area, leading to more collisions and a faster reaction rate.

increase pressure

increasing the pressure forces the gas particles coler together

catalyst

speeds up a chemical reaction BUT is not used up in the reaction