chemical bonding

elements react to form compounds by gaining or losing electrons or by sharing electrons.

when two substances react together they make a new substance and it is difficult to separate them. some atoms react by sharing electrons and we call this covalent  bonding. other ataoms react by gaining or losing electrons this leads to ionic bonding .

ionic compounds are held togethre by strong forces between the oppositely charged ions. this is called ionic bonding e.g group 2and 6 in the periodic table.

covalent bonds are formed when atoms  share electrons. covalent bonds consits of molecules but some have giant covalent structures.

the atoms in metals are arranged in regular layers.

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  • Created by: Estell
  • Created on: 01-04-12 20:12

structure and properties.

why do ionic compounds have high melting points?

ionic compound have high melting pointbecause it needs a lot of energy to break the bonds whcih holdes the giant ionic lattice.

why do ionic compounds conduct electricity when we ,elt them or dissolve them in water??

because their ions can then move freely.

which substances have low melting point and boiling pont?

substances made up of simple molecules have low melting point and boiling point.

why don't simple molecule substances conduct electricity.??

they have no overall charge so they cannot carry electrical charge.

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more notes for you!!

How do substances with giant covalent structures behave?

these substances have high melting point and boiling point.

why is diamond hard and graphite slippery??

graphite has giant structures and it contain layers of ataoms that slide over each other. diamond has a diffrent structure which is hard for atoms to slide over each other.

why can graphite conduct electricity??

because of the delocalised electrons along its layers.

why can we bend and shape metals??

because the layers of atoms in a metal can slide over each other.

why do metals conduct electricity and heat/?

 because they have delocolised electrons in them.

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continue !!

what are the relative masses of protons, neutrons and electrons/

the relative mass of proton and neutrons is 1.

what is an atoms mass number?

the mass number of an atom tells you the total number of proton and neutrons in its nucleus.

what are isotopes?

isotopes are atoms of the same element with different  numbers of neutrons.

what is reversible reaction?

in a reversible reaction the products of the reaction can react to make the original reactants.

why is ammonia important.

ammonia is an important chemical for making other chemicals e.g fertilisers.

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continue almost there!!!

how do we make ammonia.

ammonia is made form nitrogen and hydrogen in the haber process.

what do we mean by the reate of a chemical reaction?

the rate of a chemical reaction tells us how fast the reactant are turned into products.

what affects the rate of a chemical reaction.

temperature, concentration/ pressure, surface area and pressure of the catalyst. 

what is activation energy?

the minimum amount of energy that particles must have in order to react.

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continues :)

how does changing the concentration of reactants affect the rate of reaction.

increasing the concentration increases the frequency of collisions between particles increasing the reate of reaction.

how does changing the pressure of reacting gases affect the rate of reactions?

increasing the pressure of reacting gases result in particles colliding more often increasing the rate of recation.

how does catalysts affect the rate of chemical reaction?

a catalyst speeds up the rate of a chemical reaction.

what is exothermic reaction?

is where energy is transferred from the reacting substances.

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keep going!!

what is endothermic reaction?

a reaction where energy is transferred to the reacting substances.

what is electrolysis?

electrolysis involves splitting up a substance using electricity.

what is made when we electrlyse substances?

the positive ions move to the negative electrode(cathode) and the negative ions move to the positive electrode( anode).

what is the products when we electrolyse brine?

we get three products chlorine gas, hydrogen gas and sodium hydroxide gas.

why do we need to purify copper?

because it contains impurities such as silver.

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wht are solutions acidic or alkaline?

acids are substances which produce H+ ions when we add water  to them.

bases are substances that will neutralise acids.

an alkali is a soluble base which produce OH- ions when they are added to water.

how e measure acidity?

we use the PH scale to show how acidic or alkaline a solution is.

acid+ metal> slat+ hydrogen

acid+base> slat+ water

acid+alkali> slat+water

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hope it helped:) 

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