Bonding and properties Flashcards
What are bonds, and how are they formed?
Bonds are electrostatic forces (attractions between positive and negative charges) which hold atoms together.
Atoms form bonds to become more stable - by losing, gaining or sharing electrons.
The type of bond formed in a substance depends on the elements involved and their position in the periodic table.
What is the structure of an ionic compound?
Ionic compounds form giant lattice structures held together by electrostatic forces between oppositely charged ions. The formula unit of an ionic compound is determined by the ratio of metal to non-metal ions. For example, in sodium chloride (NaCl), the ratio of sodium (Na⁺) to chloride (Cl⁻) ions is 1:1, resulting in the formula unit NaCl.
NET CHARGE IS 0 - CANCELLED OUT
List all the properties of ionic compounds with small reasoning - long onee:
Brittle - when force is applied, ions shift slightly causing change in formation and repulsion (+ and - together), this causes the lattice to break.
High boiling and melting point - ionic compounds are arranged in alternating pattern, Strong electrostatic attraction , causing more energy to break bonds - higher melting and boiling point (NOTE smaller ions need more because more compact - more bonded)
Hard, crystalline solid - 3D lattice (actual arrangement varies based on ions), Multiple ‘bonds’ hold each ion in place (strong) Repeating ions = regular shaped “giant” structure
Solubility - Water’s polarity overcomes electrostatic forces in the ionic lattice, pulling ions apart. If strong enough, the ions dissolve; if not, the compound remains insoluble.
Conductivity - Ionic compounds don’t conduct electricity in solid form because their ions are fixed in a lattice, but when melted or dissolved, the ions become mobile, allowing electricity to flow.
How does the strength of a metallic bond increase?
The strength of metallic bonding increases with more valence electrons and a higher cation charge. More delocalized electrons in the sea of electrons create a stronger electrostatic attraction, making the metal stronger, the increase in atomic radius weakens metallic bonds more than extra protons strengthen them, making metals softer and lowering their melting points.
List properties of metallic compounds with reasoning.
High MP/BP - change in state requires weakening/breaking metallic bonding, the strong electrostatic attraction between delocalised electrons and cations requires lots of energy to overcome
Malleable and ductile - Metallic lattice is not fixed (unlike ionic) when force is applied, cations shift and drag delocalized electrons with them, metallic bonding remains intact (cations don’t get close enough to repel).
Good conductors - Metals conduct electricity as extremely mobile delocalized electrons repel and push each other, creating a flow of charge. They conduct heat as electrons collide with cations, transferring energy throughout the structure.
Insoluble - No ions/polar regions to attract H2O
Metallic bonding is stronger than any other attraction to molecules
Lustrous - Delocalised electrons reflect light
High density - closely packed lattice
What are alloys?
Alloys are a mixture of metals (or small amounts of non-metals). The addition of other element/s alters the properties of the original metal
EG steel (Fe + C)harder and less malleable than iron
stainless steel
(+ Cr)resistant to corrosion
What are the 2 types of covalent bonds
Covalent Network → Forms a continuous 3D network of strong covalent bonds. (SiC - keeps on going)
Covalent Molecular → Exists as separate, small molecules held together by weak intermolecular forces. (C02)
What are allotropes?
Allotropes are different structural forms of the same element, which have different properties due to their bonding arrangements.
O2 - OXYGEN GAS
O3 - OZONE LAYER
LIST STEPS TO WRITE FORMULA FOR 2 NONMETALS BONDING:
DRAW LEWISY THEN FIND HOW MANY OF ONE NEEDS TO BOND WITH OTHER - RATIO THEN SIMPLIFY IT - TEST SWAP AND DROP WITH VALENCY TO DOUBLE CHECK.
What are some properties of a diamond - 3D (network) Lattice?
All bonds are covalent (significant amount of energy needed to break bonds)
Each atom is bonded covalently to 4 others -
rigid lattice is able to withstand significant force
Insoluble - No polar regions to attract to water molecules All atoms held firmly in lattice
Doesn’t conduct electricity -Conductivity requires mobile charged particles -No ions -All electrons held in covalent bonds
What happens in Graphite – 2D (layer) Lattice?
Each carbon atom is covalent bonded to 3 others = layer lattice (hexagon arrangement)
4th electron becomes delocalized = moves throughout layer (but not between layers)
Each layer = “large molecule”, significant dispersion forces hold layers together
What are properties of Graphite – 2D (layer) Lattice?
Sublimes at v. high temperatures
Covalent bonds throughout layers
significant amount of energy needed to break bonds
Insoluble in water
No polar regions to attract to water molecules
All atoms held firmly in lattice
Conducts electricity but only in one direction (‘along’ layers) as Conductivity requires mobile charged particles, the 4th electron from each C atom is delocalized = able to move throughout layer when current is applied (but not between layers)
slipper/easy to slide layers apart (led pencil) when force is applied in same direction of layers
graphite is brittle when force is applied parallel to the layers (layers have limited thickness) not perpendicular because they just slide
name up to 10 prefies for covalent
mono, di, tri, tetra, penta, hexa, hepta, octa, nona, deca
What are the 2 types of hydrocarbons?
saturated and unsaturated
What is a alkane?
Alkanes are known as saturated hydrocarbons - only single covalent bonds between the carbon atoms of alkanes. They only contain carbon - carbon and carbon - hydrogen bonds ( straight or branched)
What’s alkanes - homologous series (straight chained only)? list properties too
A homologous series of alkanes consists of carbon and hydrogen compounds where each successive member differs by a -CH₂ unit. As the chain length increases, physical properties like BOILING AND MELTING POITNS gradually INCREASE, while chemical properties remain similar. This pattern continues indefinitely, following the general formula CₙH₂ₙ₊₂.
properties (also refer to boiling and melting above):
not soluble - non-polar
At room temperature:
the lighter alkanes (C1 – C4) are gases;
the mid-weight alkanes (C5 – C15) are liquids;
the heavier alkanes (>C15) are solids, or tars.
how do you name straight chain alkanes?
number of carbon and end in ane:
first 10 prefixes are:
meth, eth, prop, but, pent, hex, hept, oct, non, dec
(FIRST 4 MY ELEPHANT PAINTS BUTTERFLIES).
to determine hydrogens - 2*carbon + 2 (PRACTICE THESE)
