electrons and bonding Flashcards
(12 cards)
Give the number of electrons that can fill each of the first four shells
Shell 1: 2 electrons
Shell 2: 8 electrons
Shell 3: 18 electrons
Shell 4: 32 electrons
atomic orbital
a region around the nucleus that can hold up to two electrons, with opposite spins
How many orbitals make up s , p and d subshells?
How many number of electrons can fill s , p , d sub shells
s- sub shell has 1 orbital, p sub shell has 3 orbitals, d sub shell has 5 orbitals
Each orbital can hold 2 electrons
s sub shell max: 2
p sub shell max: 6
d sub shell max: 10
What is the order of filling of sub-shells for the first three shells and the 4s and 4p sub-shells in order of increasing energy?
1s,2s,2p,3s,3p,4s,3d,4p.
The first shell has the lowest energy (closest to the nucleus) and energy increases as the shell number increases. The general trend for sub-shells is that s-sub-shells have the lowest energy, then p, and d has the highest energy (apart from f-sub-shells which aren’t covered in our specification). 3d and 4s sub-shells do not follow the general trend. 4s sub-shells have a lower energy than 3d sub-shells.
ionic bonding
the electrostatic attraction between positive and negative ions
Describe how the ions are held together in an ionic crystal like sodium chloride.
Ionic compounds form giant ionic lattices, resulting from oppositely charged ions strongly attracted in all directions. For example, in NaCl, each sodium ion surrounded by 6 sodium ions
Features of ionic compounds
have high melting and boiling points
soluble in water
don’t conduct as a solid but do in liquid and aqueous states
why do ionic compounds have a high melting and boiling point
because a large amount of energy is needed to break the strong electrostatic forces that hold the oppositely charged ions together in the solid lattice. Hence, they are solid at room temp
why are ionic compounds soluble in water
many ionic compounds are soluble in polar solvents like water. this is because the polar water molecules can break down the lattice by attracting the ions and surrounding them. the slightly negative charge on oxygen atoms in water molecules are attracted to the positive sodium ions and the slightly positive hydrogen atoms attracted to negative chloride ions.
why don’t ionic compounds conduct as a solid?
-ions held in fixed positions in the lattice by strong ionic bonds. there are no mobile charge carriers.
-when ionic compounds are molten, they can conduct beuaeez the lattice breaks down and ions become mobile so can carry the charge
-ionic compounds can also conduct when they are in aqueous solution because the lattice breaks down and the ions become mobile so can carry the charge.
definition covalent bonding
strong electrostatic attraction between a shared pair of electrons and the nuclei of bonded atoms.
what is the meaning of average bond enthalpy and how can we use it?
-its a measure of covalent bond strength.
-the larger the value of average bond enthalpy, the stronger the covalent bond and more energy required to break it.
-can be used to calculate enthalpy change of reactions
