Chapter 5 Flashcards
Electrons and Bonding
What are the numbers of electrons that can fill the first four shells ?
2, 8, 18, 32
Define atomic orbital
a region of space around the nucleus that can hold up to 2 electrons, with opposite spins. Shells are made of atomic orbitals.
Define s block element, p block element and d block element
Highest energy electron is :
s electron / p electron / d electron
What type of electrons are there in the first shell ?
2 x 1s-electrons
two electrons with same energy levels
What type of electrons are there in the second shell ?
2 x 2s-electrons
6 x 2p-electrons
two different energy levels, 8 total electrons
What type of electrons are there in the third shell ?
2 x 3s-electrons
6 x 3p-electrons
10 x 3d-electrons
three different energy levels, 18 total electrons
What type of electrons are there in the fourth shell ?
2 x 4s-electrons
6 x 4p-electrons
10 x 4d-electrons
14 x 4f-electrons
four different energy levels, 32 total electrons
What shape is a s orbital
spherical shaped
What shape is a p orbital
dumbbell shaped ( figure of 8 sideways )
How many orbitals are present in an s, p,d and f subshell ?
1, 3, 5, 7
How many electrons can an orbital hold upto ?
2 ( with opposite spins due to being negatively charged and repelling each other )
What are the 5 rules by which electrons are arranged in a shell ?
Electrons added one at a time
Lowest available energy level is filled first
Each energy level must be filled before the next one can fill
Each orbital is filled singly before pairing
4s is filled before 3d
Which electrons are gained/lost when an atom becomes an ion ?
Electrons in the highest energy level
Which electrons are lost when d block elements form ions
They lose the 4s-electrons before the 3d-electrons
Why does the 4s orbital fill before the 3d orbital
4s orbital has a lower energy level than 3s orbital
Define ionic bonding
The electrostatic attraction between positive ions and negative ions / oppositely charged ions
Explanation of the solid structures of giant ionic lattices
Resulting from oppositely charged ions strongly attracted in all directions
What state are ionic compounds are room temperature and why ?
Do they have high or low melting points ?
Solids at room temp.
High melting / boiling points.
At room temp there is insufficient energy to overcome electrostatic attractive forces between cations and anions in the giant ionic lattice. High temps required to provide energy needed to overcome these forces.
Describe an ionic giant lattice
The regular arrangement of alternating positive and negative ions. Each positive ion is surrounded by negative ions and each negative ion is surrounded by positive ions.
What two factors do melting points and boiling points depend on ? Explain the relationship using the factors
Depend on ionic charges and size of ions
Charge on bond increases = Strength of ionic bond increases
Size of ions decrease = strength of ionic bond increases
Are ionic compounds soluble ?
Yes they dissolve in many polar solvents eg water
Electrical conductivity of ionic compounds. Solid vs Liquid/Aqueous states
Solid :
ions held in fixed positions in giant ionic lattice
no mobile charge carriers
no electrical conductivity
non conductors
Liquid/Aqueous :
ions free to move
ions are mobile charge carriers
electricity is conducted
Define covalent bond
The strong electrostatic attraction between a shared pair of electrons and the nuclei of bonded atoms.
What is a dative covalent bond ?
shared pair of electrons and both electrons are donated by one atom
What is the average bond enthalpy ?
it is a measurement of covalent bond strength. The energy required to break a covalent bond. The stronger the bond, the more energy is required to break the bond, so the greater the value of the average bond enthalpy.
Covalent compound properties ( usually )
low melting and boiling points
soluble in non polar solvent eg hexane ( not water )
poor conductors of electricity even when molten
How to decide whether something is ionic or covalent
know electrons in outer shell
use dots and crosses ( and then maybe triangles )
unless it’s an exception, make sure each atom ends up with 8 outer shell electrons
for elements lower down, copy element at top of group
exceptions are BeCl2, BF3, SF6
What are the three main exceptions to the rules of ionic and covalent bonding ?
BeCl2, BF3, SF6
When can expansion of the octet occur ?
only possible when n = 3 when a d sub shell becomes available.
What is the octet rule ?
Outer shell has octet ( 8 ) of electrons
Most stable arrangement for any atom
Arrangement causes unreactivity
No more electrons required to complete outer shell
