Chemistry Mid-Topic Test - Year 10 Flashcards
What is an Atom
Smallest part element can be broken down into
Consists of protons, neutrons, electrons
What is the Nucleus
Center of the atom, consists of protons and neutrons
High density, small volume
Positively charged
99.9% of mass
What are Isotopes
Atoms of same element but contains different number of neutrons in nucleus
Main difference from original element is mass
What is Electron Configuration
Way of writing amount of electrons in each shell
- First shell takes 2 electrons
- Second shell takes 8 electrons
- Third shell takes 8 electrons
- Fourth shell takes 8 electrons (Need to only know up to 2)
What happens across a period in atoms
Across a period the size of the atom decreases
- As electrons are attracted more strongly to nucleus (More protons in nucleus)
- Chance of gaining electrons and forming negative ions increases
What happens in groups in atoms
Same number of valence electrons
- Group number tells us the charge and how many valence electrons it has
They form the same number of bonds
Atoms get bigger down a group
- They hold their electrons less tightly (Even though they have more protons, there are more shells)
What happens on left hand side of periodic table
Forms positive ions
As you go down group, forms ions easier, as the valence electrons are further from nucleus (More shells), so they let go of them easier (Francium is the weakest)
What happens on right hand side of periodic table
Forms negative ions
As you go to top of group, forms ions easier, as the valences are closer to nucleus (Less shells), so they can pull in more
What is the Noble Gases Pattern
Noble gases unreactive
- Their outermost shell is always full (8 electrons, except Helium)
What is Electronegativity
Ability of an atom to attract additional electrons
As you go from left to right of periodic table, electronegativity increases
- Means the size of the atom gets smaller, increasing the attraction of electrons
- This is because the nucleus becomes more positive (Has more protons), pulling electrons in closer
As you go from up to down of periodic table, electronegativity decreases
What is a Compound
Substance made up of 2 or more different elements in fixed ratio
What are ionic bonds
Metal with nearly empty outher shell reacts with non-metal with nearly full outer shell
Where the metal gives their electron to non-metal, so both get full shells
What is the ionic bonding
Each ion in ionic compound is held in place by electrostatic attractive forces
- Held together as opposite ions attract (Anions & Cations)
Ions form crystal lattice made of ionic bonds
- Each positive ion surrounded by 6 negative ion, vice versa
- Keeps formation in place
What are ionic compounds
Compounds that consist of ions
Consists of metal and one or more non-metals
Properties of ionic compounds & ionic bonds
Conductive
Hard
High melting point & boiling point
Soluble
Brittle
- Force applied = Puts positive ions next to eachother, shattering the compound
– Due to repulsion of like charges
– Example: Salt (NaCl)
Solubility process of ionic compounds
For Ionic Solids That are Soluble:
Lattice structure of ionic bonds disrupted by water molecules
After dissolving, individual ions are scattered through solution
Flow of Charge in Ionic Compounds
Solids:
Ions in lattice fixed in position
They don’t move = No charge flows
Liquid:
Ions in lattice can move
Charge flows = Conducts electricity
Ions go towards their opposite charge (Positive to negative)
What are Covalent Bonds
Form when two non-metal atoms with nearly full outer shells share electrons
Neither one gives away an electron
Diagrams mainly shown through electron dot diagrams
They make molecules
- Specific atoms joined by sharing electrons
How are Covalent Bonds Formed
Non-Metals hold onto valence electrons
- Can’t give them away electrons to bond
- Though still need noble gas configuration
- They get it by sharing valence electrons with each other
– = Both atoms get to count electrons toward noble gas configuration
What are the 2 kinds of molecules formed
Molecular compounds
Diatomic Molecules
How are Molecular Compounds formed from covalent bonds
Sharing electrons of different elements
Eg. NaCl, Sodium and Chloride share atoms
Low melting & boiling points
Molecular formula shows type & number of atoms in molecule
- Not ratio, actual amount
- Doesn’t tell you how atoms arranged
How are Diatomic Molecules formed from covalent bonds
8 elements that always form molecules
- Elements: Hydrogen, Nitrogen, Oxygen, Fluorine, Chlorine, Bromine, Iodine, Astatine
– All the -ogens, -ines
– Basically, Oxygen by itself means O2
- Easy way to remember, 1 + 7 pattern on periodic table
What are Single Covalent Bonds
Sharing of two valence electrons
Only between non-metals, and hydrogen
Difference from ionic bond because they form molecules
- Two specific atoms joined
- In ionic solid, you can’t tell which atom electrons moved from/to
What are Multiple Covalent Bonds
Atoms that share more than one pair of valence electrons
- Double bond = Atom shares two pairs (4) of electrons
- Triple bond = Atom shares three pairs (6) of electrons
How to figure out if you need multiple Covalent Bonds
Add up all current valence electrons
Add up all needed electrons for noble gas configuration
Subtract
Divide by 2
Gives bonds
If bonds > atoms, need multiple bonds
How to figure out if you need multiple Covalent Bonds
Add up all current valence electrons
Add up all needed electrons for noble gas configuration
Subtract
Divide by 2
Gives bonds
If bonds > atoms, need multiple bonds
What are Ions
Electrically charged, formed when atoms gain / lose electrons to fill shell
Fills shell to become more stable
Electrons that are gained by negative ions came from an ion
- That ion released an electron and became positive
What are Cations
If atom loses electrons to fill shell = Positive ion (Cation)
- Forms on left hand side of periodic table
Atoms that have few valence electrons that don’t attract as much
What are Anions
If atom gains electron = Negative ion (Anion)
- Forms on right hand side
Atoms with many valence electrons gain electrons forming negative ions
What are Ionic Substances
When an element from the left hand side joins with element from right hand side, the left hand side gives electron to right hand side
How do you name Metallic Substances
Element name
How to name Covalent Molecular Substances
Element further left named first, keeps its normal name
- If two elements in same group, element further down named first
Element further right (Higher if in same group), named second
- End of its name changed to end in ‘-ide’
– Eg. Fluoride, Oxide, Sulfide, Bromide
What are the Prefixes for naming Covalent Molecular Substances
Used to indicate if more than one element present in molecule
- 1 = Mono
- 2 = Di
- 3 = Tri
- 4 = Tetra
- 5 = Penta
If first element has one atom, prefix mono not used
Molecules composed of one element only, get name of original element
How to name Ionic Compounds
Metal / Positive Ion named first
- Keeps normal name
Non-Metal / Negative Ion named second
- End of its name changed to end in ‘ide’
– Eg. Fluoride, Oxide, Sulfide, Bromide
How to write formulas for Metallic Elements
Single symbol that does not indicate number of atoms present
- Eg. Na, Al, Fe
How to write formulas for Ionic Compounds
Positive ion (Usually metal ion) written first
Negative ion (Usually non-metal ion) written second
Number of each ion adjusted so that positive charge = Negative charge
- Subscripts used to indicate number of ions present
–Shows ratio, not actual amount
- Use ‘drop and swap’ method
How to write formulas for Covalent Substances
Element further left named first
- If two elements in same group, element further down named first
Element further right (Higher if in same group), named second
Number of each ion adjusted so that charges are equal
- Subscripts used to indicate number of ions present
- Use ‘drop and swap’ method
Dissolving Substances Rule
Attractive forces between substance dissolving (Solute) & water (solvent), are stronger than attractive forces between solutes alone
- If happens = Solute dissolves
What are Solutions
Form when particles of solute (Particles) enter the solvent (Water)
Have uniform properties
May be coloured, but always clear
What happens when you put a battery into water
If you put battery into water
- All positive ions go to negative electrode (Negative battery side)
- All negative ions go to positive electrode (Positive battery side)
What is a precipitation reaction
Insoluble solid that can form as part of reaction between two ionic solutions
Solubility of compound can be predicted from solubility rules
What is Solubility
Ability for a solute to dissolve in a solvent to make a solution
Can use solubility table to check if compounds form solutions or precipitates
