Topic 4: Chemical Bonding
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Why do atoms bond?
To get full outer electrons
What are ionic compounds made from?
Made from metals and non metals
What are covalent compounds?
Only Non metals
When are ions formed?
When atoms lose or gain electrons to obtain the stable electron arrangement of a noble gas
When are ionic compounds formed?
When a metal reacts with a non metal. During this process electrons are transferred from the metal to the non metal. And they become stable
What type of ions do metals and non metals make?
Metals make positive ions Non metals make negative ions
What does the charge of an ion mean for the valency?
The charge is the valency
When do atoms achieve a noble gas electron arrangement?
When they react, but they do not become noble gasses. (Because the protons (atomic number) determines the identity of the element)
What happens to the number of protons when elements react?
The number of protons doesn’t change
Why do ions have charge?
They do not have an equal number of protons and electrons
What is the ion-electron equation?
For metals: Na—> Na+ + e- For non metals: Cl + e- —> Cl- For metals you put the unchanged first and then you write what needs to be done to get the ion to be the same as it was before For non metals put what is needed to be done to turn it into an ion before the arrow Basically just write what needs to be done with the electrons to make it ionic or not
What is it called when elements have the same electron arrangement after forming an ionic bond?
Isoelectronic
What are ionic bonds? (Definition)
The electrostatic attraction between positive and negative ions
What do ionic compounds form lattice structures like? structure
Of oppositely charged ions with each positive ion surrounded by negative ions and each negative ion surrounded by positive ions
What happens when an ionic compounds lattice is formed / what does it cause?
There are millions of positive and negative ions created.
What do ions have that make them form ionic bonds?
Opposite charges; the ions attract each other and form an ionic bond
Why are ionic compounds called that?
Because they are composed of ions and the ions are held together by ionic bonds
How do ions arrange themselves when an ionic compound is formed / what form do they take
Into an ionic lattice
Ionic formulae
Write the formula first without ions Then look in the data booklet for the ions of the elements then put them in No need to switch or change them Put brackets around them only if there are multiple of the same type of ion (Never cancel down charges, always cancel valency numbers, crossed valency numbers are always outside of the brackets and never write an ionic formula for a covalent)
What would melting point/boiling point of liquids or gases almost always be? (Not specific general)
Less than room temperature
Do ionic compounds usually have high or low melting/boiling points?
High
Why do ionic compounds have high melting/boiling points?
Because strong ionic bonds must be Broken in order to break up a lattice (The bonds are very strong so it takes a lot of energy to break them up)
Why are many ionic compounds soluble in water?
Because as they dissolve the lattice structure breaks up allowing water molecules to surround separated ions
What are substances that allow a current to flow called?
Conductors