Atomic bonding and structure Flashcards
How are all elements organised?
Into a grid structure called the period table
What are the columns in the periodic table called?
Groups
What are the rows in the period table called?
Periods
What do elements in the same group have?
Similar chemical properties (they react similarly with certain chemical substances)
What are the three names groups?
Group 1- alkali metals
Group 7- halogens
Group 8 (or 0)- noble gases
How many elements in the periodic table don’t exist as single atoms?
7
What are elements called when they don’t exist as single atoms?
Diatomic
Why are elements called diatomic?
They exist in molecules of two atoms each
Name the seven diatomic elements
H2, N2, O2, F2, Cl2, Br2, I2
What are atoms made up of?
3 types of subatomic particles
Protons
Neutrons
Electrons
What charge do protons have?
Positive
What charge do neutrons have?
Neutral (0)
What charge do electrons have?
Negative charge
Where are protons located in an atom?
Nucleus
Where are neutrons located in an atom?
Nucleus
Where are electrons located in an atom?
Electron shells
How can each atom be described?
Two numbers
No. of protons and mass number
What is the number of protons also known as?
Atomic number and it’s unique to every single element
What is the mass number?
No. of protons + neutrons
Why are atoms neutral?
Number of protons is the same as number of electrons
What does energy levels mean?
Electrons are arranged around the nucleus in discrete (separate) shells
What is the outermost shell containing e- called?
Valence shell
What is the e- called that resides in the valence shell?
Valence e-/ outer e-
Why is the smallest shell filled in first?
Closest to the positive nucleus (which e- are attracted to)
What are noble gases the only element to have?
Full outer shells
What is the group number the same as?
No. of valence e-
What is the period number the same as?
The no. of occupied e- shells
What is an ion?
Charged atom
When is an ion formed?
When an atom loses or gains e-
Why do atoms lose or gain e-?
To get a full outer shell. This makes the more stable
What do ions have the same electron arrangement as?
The nearest noble gas
What do non-metal atoms gain and form?
Gain e-, form negative ions
What do metal atoms lose and form?
Lose e- and form positive ions
What are isotopes?
Atoms of the same atomic number (same element) with different mass numbers.
No. of p+ is the same, but no. of n° is different
What can use nuclide notation to do?
Distinguish between different isotopes
What is carbon dating?
Using carbon-14 atoms to find out the age of long-dead organisms.
What is carbon-14 and what does it mean?
Radioactive.
This means that when a living organism dies, the carbon-14 atoms it contains gradually decays into more stable carbon atoms
What are not all isotopes?
Equally abundant.
Generally, stable isotopes are abundant, while unstable isotopes are found only in trace amounts
What does isotopes stability depend on and why does this happen?
The number of neutrons in the nucleus. Too many or too few will make it unstable.
This happens because neutrons play an important role in minimising repulsions between positively charged protons. Since neutrons themselves have no charge, they act as a ‘buffer’ between protons. play an important role in
How many isotopes does copper have?
Two 63Cu and 65Cu
What is relative atomic mass?
Average mass of all isotopes of an element taking into account their relative abundance
When can RAM be calculated?
If the abundance of each isotope of an element is known
What are noble gases?
Monatomic
What does monatomic mean?
They exist as single atoms
Why are noble gases monatomic?
They already have full outer shells which makes them very stable
How can other elements obtain stable e- configuration?
The can form ions by losing or gaining electrons, or form covalent bonds to achieve full outer shells and become more stable
When does a covalent bond form?
When two positive nuclei are held together by their common attraction for a shared pair of electrons.
Where do covalent bonds usually form?
Between non-metal atoms
What can we use a dot and cross diagram for?
Show how e- are arranged in molecules
What do dot and cross diagrams only show?
How the valence e- because they are only ones involved in bonding
Why are atoms overlapped in dot and cross diagrams?
To give each atom a share of enough e- to give them a full outer shell
How are e- drawn in dot and cross diagrams?
Dots for one atom and crosses for the other with shared pairs of e- drawn in the overlap area
What are structural formulae used to show?
The number of bonds between atoms in a molecule
What do each bond between two atoms represent?
One pair of e- being shared
What can covalent molecules adopt?
A number or common shapes
What can we often do when predicting a shape of a compound?
Often we can predict a shape of a compound by counting the no. of atoms in the molecule
What do simple lines represent when drawing 3D shapes on paper?
These bonds are on the same plane as the paper
What do dashed lines represent when drawing 3D shapes on paper?
These bonds are behind the paper
What do wedges represent when drawing 3D shapes on paper?
These bonds are in front of the paper (pointing towards you)
What will all two atom molecules be and most molecules containing double/triple bonds
Linear
What often are 3 atom molecules containing only single bonds?
Angular
What is the reason for angular shapes?
Is usually e- pairs nor engaged in bonding repelling shared e- pairs, changing the shape of the molecule
What shape do 4 atom molecules adopt?
Trigonal pyramidal
What is the most common trigonal pyramidal?
Ammonia
What shape do molecules containing boron adopt?
Trigonal planar shape
What shape do molecules containing 5 atoms often adopt?
Tetrahedral structure
In covalent substances how are atoms held together?
Covalent bonds
What are the two types of covalent structures?
Molecular
Network
Do covalent substances conduct electricity?
No except for graphite
What are covalent molecular elements and compounds made up of?
Discrete molecules
What does each discrete molecule contain?
Few atoms bonded together
Do covalent molecular elements have strong or weak forces of attraction between molecules?
Weak. They are broken when a substance boils (covalent bonds are not broken)
What are the properties of covalent molecular structure?
Low melting and boiling points due to weak attractions between molecules
Can be gas, liquid or solid at room temp
Some can dissolve in water
What temperature is room temperature?
25°C
What happens to molecular substances that don’t dissolve in water?
They will usually dissolve in other solvents, e.g hexane
What are covalent network elements and compounds made up of?
Thousands of atoms bonded together
What are the only network elements?
Boron, silicon and carbon
Silicon carbide and silicon dioxide are what?
Network compounds
What is the major component in sand and glass?
Silicon dioxide (SiO2)
What is the formula for all covalent network compounds?
Ratio of different atoms in the giant structure
What are the two common network forms of carbon?
Diamond and graphite
What structure does diamond have compared to graphite?
A more regular structure with only strong covalent bonds throughout
What are the properties of covalent network structures?
High melting + boiling points due to strong covalent bonds between all atoms
Solid at room temp
Doesn’t dissolve in any solvent
Hard, durable and extremely unreactive
What are ionic substances usually?
Compounds made of metals and non-metals (eg. NaCl)
What do ionic compounds form instead of molecules?
Huge lattice structures
What is an ionic lattice?
A grid-like arrangement held together by strong electrostatic attraction between + and - ions
Why do ionic compounds have high melting + boiling points?
They are held together by strong ionic bonds
What is required to break ionic bonds?
A lot of energy (high temp)
What are ionic substances at room temp?
Solids
What are ionic compounds often in water?
Soluble
What must a substance require to conduct electricity?
Flow of charged particles
Why can’t ions move freely in ionic solids?
They are locked in a lattice
What happens if an ionic solid is molten or dissolved?
It will be able to conduct as ions will be able to move freely
What is the best way to determine the type of bonding between metallic, covalent network and ionic substances?
Conductivity test
What state do metals conduct?
Solid and liquid
What state do ionic compounds conduct?
Molten or dissolved
What state do covalent networks conduct?
They don’t at all except graphite
