1) Key Concepts in Chemistry Flashcards
What are compounds?
Combined atoms of different elements
What is the smallest piece of an element that can exist?
An atom
What are the key features of chemical compounds?
Compounds are broken up or formed
At least 1 new substance is created
Measureable energy change
No atoms are created or destroyed
What type of equation must be balanced?
Symbol equations
What is the order of atomic models?
Dalton’s model
Thomson’s plum pudding
Rutherford’s nuclear model
Modern model
What is the atomic number?
Number of protons in the atom
What is the mass number?
Number of protons + neutrons
What is the top number of an atom?
Mass number
What are isotopes?
Atoms with the same number of protons but a different number of neutrons
What are the isotopes of hydrogen?
Protium
Deuterium
Tritium
What is the name for a specific nucleus that contains a certain number of protons and neutrons?
Nuclide
What did J.J.Thomson discover?
Electrons
What was J.J.Thomson’s model?
Plum pudding model
What did Rutherford discover?
Alpha particles could bounce off atoms
Atom’s mass concentrate in centre
Protons
What was Rutherford’s model?
Nuclear model
Who discovered neutrons?
James Chadwick
What is the relative atomic mass?
The average mass of all of the isotopes of an element
What is the formula for Ar?
(Isotope abudance x isotope mass number) / isotope abundance
What does Ar mean?
Relative atomic mass
What is the isotope abundance?
How often each isotope of an element is found
What are the rows of the periodic table called?
Periods
What are the columns of the periodic table called?
Groups
What does the group number equal?
The number of electrons in an atom’s outer shell
Who was the first to devise a periodic table?
John Newlands
Who predicted the undiscovered elements of the periodic table?
Mendeleev
How do we rank elements today?
By their atomic number (number of protons)
Where are metals found on the periodic table?
The left side
What happens when metals react?
They lose 1 or more electrons to form positive ions
What are properties of metals?
High melting and boiling points
Good conductors of heat and electricity
Solids at room temperatrue (except mercury)
Where are non-metals found on the periodic table?
The right side
What happens when non-metals react?
They gain electrons to form negative ions
Or share electrons to form neutral molecules
What are properties of non-metals?
Lower melting and boiling points than metals
Often found as gases
Generally do not conduct heat or electricity
How does energy change as you get closer to an atom’s nucleus?
Closer to nucelus = lower energy level
What is the filled electron configuration?
2,8,8
What is the difference between molecules and an element?
Molecules are a substance with two or more atoms (O2)
Elements are pure substances of the same atom (O)
What can dot and cross diagrams show?
Electrons being transferred and ions formed
What do square brackets and a charge represet in dot and cross diagrams?
Ions
What is a cation?
A positive ion
What is an anion?
A negative ion
What does a cation have?
More protons than electrons
What does an anion have?
More electrons than protons
What is ionic bonding?
When atoms trade electrons to both have full outer shells
What happens to group 1 metals during ionic bonding?
They lose 1 electron
What happens to group 2 metals during ionic bonding?
They lose 2 electrons
What happens to group 6+7 non-metals during ionic bonding?
They gain electrons
What happens to group 0 noble gases during ionic bonding?
They are unreactive as they have a full outer shell
How are cations created?
When an atom or molecules loses electrons
How are anions created?
When an atom or molecule gains electrons
What happens to an atom’s charge if it gains electrons?
Negative charge
What do ionic compounds made from 2 different elements end in?
-ide
What do ionic compounds made from 3 or more different elements end in?
-ate
What does K+ and O2- form?
K2O
We need two K+ ions to cancel out the 2- charge of the oyxgen
When do we use brackets in ionic compound formulas?
When there are multiple groups of atoms
What is the overall charge of an ionic compound formula?
0
What are ionic lattices?
Giant structures held together by strong electrostatic forces between cations and anions
What are electrostatic forces also called?
Ionic bonds
When are covalent bonds formed?
When 2 non-metals share pairs of electrons
Why are covalent bonds strong?
The shared electrons are attracted to the nucelus of both atoms
What can covalently bonded structures be?
Small molecules
Large molecules
Giant covalent structures
How do double and triple bonds compare to single covalent bonds?
They are stronger and require more energy to break
What group of elements is joined by triple bonds?
Group 5 as each atom needs to gain 3 electrons to obtain a full outer shell
What are properties of ionic compounds?
High melting and boiling points
Don’t conduct electricity when solid
Conduct electricity if liquid or in solution
Why can’t solid ionic compounds conduct electricity?
The ions in the lattice are fixed in shape
What are intermolecular forces?
Weak forces found between small molecules
How strong are intermolecular forces?
Weak and easy to break
What does weak intermolecular forces mean for small covalent molecules?
They have low melting and boiling points
Often liquids or gases at room temperature
What are intramolecular bonds?
Strong covalent bonds found within small molecules
How does the size of a molecule affect the attraction to other molecules?
Bigger molecules attract other molecules with stronger intermolecular forces
What are properties of giant covalent structures?
No specific formula
Very high melting points
1 large molecule
Why don’t giant covalent structures have a formula?
They can be any size
What ways can you represent covalent bonds?
Lines
Ball and stick
Dot and cross with shells
Dot and cross without shells
What is a limitation of ball and stick diagrams?
Atoms are much closer than the diagram shows
What is a limitation of dot and cross diagrams with shells?
It shows electrons differently for each atom when they are actually the exact same
What properties does diamond have?
Doen’t conduct electricity
Covalent bonds
High melting point
Hard
How many other carbon atoms is each diamond carbon atom bonded to?
4
What is an allotrope?
A form of an element
What are properties of graphite?
Soft
Covalent bonds
Conducts electricity
How many other carbon atoms is each graphite carbon atom bonded to?
3 creating 1 delocalised electron
Why is graphite soft and used as a lubricant?
Carbon atoms form layers of hexagonal rings with weak intermolecular forces keeping the layers together
What are fullerenes?
Molecules of carbon atoms that take up hollow structures
What is the structure of fullerenes?
Usually hexagonal rings
Can be pentagonal or heptagonal
What is buckminsterfullerene?
A spherical shape
First fullerene discovered
What are uses of fullerenes?
Catalysts
Lubricants
Drug transport vehicles to our bodies
What are carbon nanotubes?
Cylindrical fullerenes
Why are cyclindrical fullernes strong?
Strong covalent bonds between carbon atoms
What are uses of cylindrical fullerenes?
Electronics
Nanotechnology
Strengthening materials
What is the formula for buckminsterfullerene?
C60
What is the relative formula mass the sum of?
All relative atomic masses of each atom in the formula
What is the empirical formula?
The simplest ratio of ions possible
What is the molecular formula?
The actual amount of atoms which make up a molecule
What is the molecular and empirical formula for glucose?
C6H12O6
CH2O
What are the steps for the experiment for calculating empirical formula?
1) Measure mass of solid going to be reacted
2) React solid with oxygen in air by heating
3) Find mass of product
4) Calculate mass of oxygen gained (final mass - initial mass)
5) Use mass of solid and oxygen to calculate empirical formula (divide mass by Ar)
What units can concentration be measured in?
g / dm^3
mol / dm^3
What is the formula for concentration?
concentration (g/dm^3) = mass (g) / volume (dm^3)
What is the Avogadro constant?
6.02 x 10^23
What is 1 mole of a substance equal to?
The relative formula mass (Mr)
If the relative atomic mass of carbon is 12, what is the mass of 1 mole of carbon?
12g
What is the equation for moles?
Moles = mass / Mr
What is a limiting reactant?
A reactant that is completely used up
How do we reduce the uncertainty of results?
Take multiple reading and calculate an average
