Topic 2 - Structure and Bonding Flashcards
bonds
forces of attraction that can hold atoms together
when are atoms more stable
when they have a full outer shell
how do you make atoms more stable
by transferring electrons between atoms forming charged particles called ions
ion
an atom or group of atoms that carries a positive or negative electric charge as a result of having lost or gained one or more electrons
cation
when the atom looses an electron and forms a positive ion
anion
when an atom gains electrons and forms negative ions
ionic bond
formed from the electrostatic attraction between oppositely charged ions in a chemical compound
if an atom (e.g. Mg) looses 2 electrons, how do you write the atom symbol
Mg2+ because you lost electrons so the atom turns positive
how are ionic compounds formed
from the loss and gain of electrons
how are ionic compounds held together
by the strong electrostatic forces of attraction between oppositely charged ions
lattice structure
a regular repeating arrangement of ions
when solid what does ionic compounds form
crystals
how do you work out an ionic formulae
use the cross over method
sodium sulphate contains Na+and S2-, what’s the ionic formulae
Na+ S2-
✖️
Na2- S+
= Na2S
polyatomic ion
set of two or more atoms ((e.g. (SO4)2-)
how do you know the ion is polyatomic and contains oxygen
ion name ends in ‘-ate’ or ‘-ite’
at what state can ionic compounds conduct electricity
once melted or dissolved in water
what two things have to happen for a substance to conduct electricity
- must be charged particles
- these particles must be free to move
name the process to create an ionic bond
the ions loose or gain and electron to each other and produce oppositely charged ions; these ions are then attracted to each other by electrostatic forces forming an ionic bond (this whole thing is an ionic compound)
in an electric current, which way do the anions move
to the anode (positive electrode)
in an electric current, which way do the cations move
to the cathode (the negative electrode)
how do you show the number of each element bonded together in a simple molecule
using a molecular formula
where are convolent bonds found
between two non-metals
how are convent bonds formed
two atoms share an electron to create a full outer shell - this makes the atom more stable
how can we show a covalent bond
using dot and cross diagram
what’s a double covalent bond
where atoms share two pair of electrons to fill their outer shells
in a molecule what is the bond between the positive nuclei and the negative electrons
electrostatic forces of attraction
molecule
two or more atoms connected by COVALENT bonds
in group 1, what’s the charge of the elements
+1
in group 2, what’s the charge of the elements
+2
in group 3, what’s the charge of the elements
+3
in group 5, what’s the charge of the elements
-3
in group 6, what’s the charge of the elements
-2
in group 7, what’s the charge of the elements
-1
in group 8/0, what’s the charge of the elements
0
what are the WEAK forces of attraction between molecules
intermolecular forces
monomers and what can it form
small simple molecules that can be joined in a chain to form a polymer
properties of simple covalent molecules
low boiling and melting points due to weak intermolecular forces
allotrope
different form of the same element
what are the different allotropes of carbon
- diamond
- graphite
- graphene
- fullerene (C60)
how is a fullerene (C60) structured and its properties
- each carbon atom is covalently bonded to 3 other carbon atoms
- spherical shape
- low melting point due to weak intermolecular forces
- soft and slippery
how is graphene structured and its properties
- it’s a sheet of carbon atoms (one atom thick) with 3 covalent bonds between each atom which forms a hexagon - you can roll this up to form a tube
- good electrical conductors as it allows free electrons to move across its surface
giant covalent molecular structures
huge three dimensional networks of carbon atoms linked together by covalent bonds
giant covalent molecular structure examples and properties (of carbon)
- diamond and graphite
- high melting points because of the many strong covalent bonds that need to be broken to melt the solids
- very strong
how many covalent bonds are there for each carbon atom in graphite
3
how many covalent bonds are there for each carbon atom in diamond
4
graphite structure
layered structure (sheets of graphene that are held together by strong covalent bonds) that are held together on top of one another by weak forces or attraction meaning they’re able to slide over each other - making graphite soft
why can graphite carry an electrical current
- because it only has 3 bonds for each carbon atoms meaning there is one electron that is not being used in covalent bonding
- this one electron is called a delocalised electron (free to move around)
- this means it’s free to move and carry a current
diamond structure and properties
- network of carbon atoms in a tetrahedral arrangement, joined by strong covalent bonds
- very hard
why can metals conduct electricity
- because metal’s outer shell electrons are lost from each atom and become free to move randomly throughout the metal
- when voltages applied between two points on a piece of metal these delocalised electrons will flow towards the positive side which transfers energy and forms an electrical current
metallic bonding
electrostatic attraction between the positive metal ions and the negative delocalised electrons
why do metals have high melting and boiling points
because the metallic bonding is so strong it needs a lot of energy to break these bonds
why are metals malleable (they can be hammered or rolled into shape without shattering)
because when you hit the metal the layers of ions slide over each other and the ‘sea’ of electrons hold the ions together that’s why it changes shape instead of breaking
how do you know when the metal can conduct more or less electricity
because of the charge of the metal (e.g. +1 or +2)
- this +1 means it contributes 1 delocalised electron and +2 means it contributes 2 delocalised electrons
- the element that contributes more electrons conducts more electricity
what are the positives and negatives for showing covalent bonds in a dot and cross diagram
positives:
- show how electrons shared in covalent bonds
negatives:
- do not show the structure formed
- they suggest that the electrons in different atoms are different when they are actually the same
what are the positives and negatives for showing covalent bonds in a 3D ball and stick model
positives:
- shows which atoms are joined together
- shows the shape of the structure
negatives:
- show atoms too far apart
what is released when bonds form
energy
when do non-metal make endings change to -ide
when they form negative ions
What does it mean if an ion ends in -ate or -ite?
It contains oxygen as well as another element
what enables ionic compounds to conduct electricity
charged ions that are free to move (NOT ELECTRONS)
what state does the iconic compounds have to be in to conduct electricity
molten or dissolved in water (in aqueous solution)
what is an electric current?
Flow of charged particles
how does the electrical conductivity increase?
When the number of delocalised electrons increase
What are the 4 different types of bonding
- ionic
- simple molecular (covalent)
- giant covalent
- metallic
