Bonding and structure Flashcards
metallic bonding what are the atoms arranged in?
Crystalline structure where the positive atoms are surrounded by a sea of electrons
What holds structure in place in metallic bonding?
Its ELECTROSTATIC ATTRACTION of pos atoms and neg outer electrons that hold structure in place
What gives the most metals high mp and bp and what is the rule for this?
The strong electrostatic attraction.
The higher the mp the stronger the electrostatic attraction
What happens if one electron (electricity) is inserted into end of a metal and what does this mean for the metal?
An electron is ejected at the other side. It can conduct electricity.
Why can metals be bent
As atoms are all same size and in an ordered structure, metals can be bent, know as malleability
Covalent bonding
Atoms share pairs of electrons. The covalent bond is a result of 2 pos nuclei being held together by their common attraction for the shared pair of electrons/ the electrostatic attraction between pos nuclei and neg shared electrons
Are electrons shared equally in covalent bond?
Yes
Why do atoms move together?
The electrons orbit around the nucleus are neg charged and nucleus is pos. the covalent bond is created when neg electrons of one atom are attracted to pos charged nucleus of another atom.
Why do atoms eventually stop moving towards each other?
The attraction pulls the atoms together until pos nuclei start to repel each other, it is then balance is reached.
What is ionic bonding and what does it create?
Ionic bonds are the electrostatic attraction between pos and neg ions. Ionic compounds form lattice structures of oppositely charged ions
What is a London Dispersion Force of attraction between
Between monatomic atoms and small discrete molecules
What is the force caused by LDF?
Force is caused by uneven distribution of constantly moving electrons around the nuclei of atoms. The atom has an electron deficient side which is very slightly negative. This is caused by movement of electrons in atoms.
Are LDF easily broken and what element and compounds can they be found?
Yes. Elements and compounds with very low melting and boiling points
Halogens
Group 7 and they kill bacteria
Alkalis
Group 1 and are very reactive
alkaline earth metals
group 2
Valency of groups and charge
g1: 1 1+
g2: 2 2+
g3: 3 3+
g4: 4 4+or-
g5: -3 -3
g6: -2 -2
g7: -1 -1
What accounts for higher melting and boiling points within LDF?
As you go down for instance group 7, the molecules get bigger with more electrons meaning neg dipoles are stronger thus melting and boiling points increase.
What does LDF cause the formation of?
Temporary dipoles
What are the diatomics
H2
N2
O2
F2
Cl2
Br2
I2
What are known as covalent molecular structures?
H, O, N, P, S, halogens, Chlorine nanotubes and fullerenes
Give an account of the covalent molecular of nitrogen
Most common gas in air (80%). 2 nitrogen atoms held together by 3 strong covalent binds. N molecules held together by weak LDF.
How can LDF increase in strength at lower temps?
LDF increase in strength at lower temps due to decrease in molecular vibration
What is not affected in the LDF whether covalent molecules are solid, liquid or gas?
Strong covalent bond holding atoms together is not affected
What elements can bond in covalent network structure?
Boron, carbon and silicon
Why does graphite conduct
Unlike diamond the carbon atoms in graphite are only bonded three times. This leaves a mobile electron (delocalised electron) to conduct electricity which is found in-between the graphite layers.
Why do noble gases not bond/react?
Due to outer electrons having a stable octet, with exception of helium which has filled outer shell of 2 electrons
What happens when electricity passed through a noble gas?
When electricity passes through a noble gas they glow and are used in advertising lighting and found inside bulbs and strip lighting.
What are intramolecular bonds?
Bonds which join atoms within the molecule
What are intermolecular bonds?
Bonds which join individual molecules
WHAT ARE PROPERTIES IF COVALENT BONDING (INCLUDING NETWORK) RELATED TO CHANGE OF STATE?
VERY high mp and bp which require intermolecular bonds to be broken for a change of state to occur.
What are properties of London Dispersion Forces related to a change of state?
Very low melting and boiling points which require intermolecular bonds to be broken down for a change of state to occur.
What have higher melting and boiling points the left hand side or the right hand side of the periodic table?
Higher on the left of the periodic table and fall dramatically for elements on the right as the type of bonding changes.
How does reactivity differ in group 1 and why is this?
As you move down group 1 there is an extra shell of electrons being added. This makes the attraction between the outer electron and the positive nucleus weaker, therefor easier to remove the outer electron. Hence more reactive the further you go down.
What do the halogens form when they accept electrons?
hallide ions
How does reactivity differ with the halogens and why is this?
The halogens reactivity decreases the further they are down the table. This is because the halogen molecule with the more exposed nucleus , has the greater ability to attraction and is therefore more reactive.
What is the test for saturated and unsaturated hydrocarbons?
The bromine water test - unsaturated will decolourise the bromine water due to the double bond whereas saturated will not decolourise the bromine water.
Q
Why does the H+ ion not exist?
H+ has no electrons
What is the reaction of the first ionisation energy of sodium?
Na(g) = Na+(g) + e-
Why does the first ionisation energy down a group decrease?
The outermost electron being removed is further from the nucleus and increased shielding down the group.
How can you decrease the activation energy?
By adding a catalyst