chemistry term2/3

periodic table

periodic table

an ordered arrangement of all 118 known elements. The elements are arranged in order of their atomic number (number of protons). Every time you move an element to the right, the proton number increases by 1

predicting chemical properties

all elements in a column have the same number of electrons in their outer shell, they have similar chemical properties. This means they will all react in similar ways.

groups

the name of columns of a periodic table. The number of the column is equal to the amount of electrons on the outer shell.

periods

the name of rows of a periodic table. The table is ‘periodic’ because elements with similar properties occur at regular intervals, i.e. periodically. Therefore, the rows of the periodic table are called periods.

John Newland

the first chemist to devise a periodic table. His periodic table was ordered by the weight of the element. However, the table was incomplete, and some elements were placed in the wrong groups.

Dmitri Mendeleev

The man who created the modern day periodic table. He realised that there may be undiscovered elements. He added gaps to Newlands’ table to account for undiscovered elements. He even predicted the properties and masses of these undiscovered elements!

metals

They are found on the left of the periodic table because they have few electrons in their outer shell. When they react, they lose 1 or more of these negatively charged electrons to form positively charged ions. They also commonly react with oxygen to form oxides

Properties of metals

.High melting and boiling points

.good conductors of heat and electricity.

.They are all solids at room temperature apart from mercury.

Non-metals

They are found on the right of the periodic table because they have many electrons in their outer shell. When they react, they either Gain electrons to form negatively charged ions or share electrons to form neutral molecules (covalent bonding)

properties of non-metals

.lower melting point

.low boiling point

electronic structure

Electrons fill an atom's shells in order of increasing energy. The closer a shell is to the nucleus, the lower its energy level, so the first shell that is filled is the closest to the nucleus.

electron shells

Electrons have fixed positions in atoms called xxx. xxx go around the atom's nucleus.

electron configuration

A way tells us how an atom's electrons are organised.

.The inner-shell (closest to the nucleus) can have a maximum of 2 electrons and the next two shells can have a maximum of 8 electrons. Any extra electrons are then put into a next shell.

key feature of a chemical reaction

.An energy change that can be measured

.At least one new substance is created

.If compounds are broken up or formed.

Key features of a physical change

.No new substance is formed.

.Reversible change

Chemical property of substance remains the same

.Change in colour, shape, size, and state

alkali metals

.group 1 metals

.malleable

.can conduct heat and electricity

.highly reactive

.low density and melting points

why group1 metals are highly reactive

They are highly reactive because they give away their electron faster to form a positive charge.

transition metals

compared to alkali metals, they have:

.higher melting points

.higher density

.lower reactivity

properties of transition metals

.can form ions with different positive charges.

.are often used as catalysts as they easily lend and take electrons from other electrons.

.can form colourful compounds.

types of chemical bonds

atoms can for 3 types of bonds, ionic bonding, covalent bonding or metallic bonding.

ionic bonding

a bonding which involves an attraction between oppositely charged ions. These bonds are found in compounds made of metals and non-metals.

covalent bonding

a bonding which involves 2 non-metal atoms sharing 1 or more pairs of electrons. These bonds are found in most non-metal elements and in compounds of non-metals. The bond is so strong because the electrons are attracted to the nucleus

metallic bonding

a bonding which involves an attraction between positively charged ions and negatively charged, delocalised electrons. These bonds are found in metals and alloys (mixtures of metals and other substances).

delocalised atom

atoms on the outer shell that are free to move

dots and cross diagrams

a diagrams that shows electrons being transferred and ions being formed. Dots represent electrons from 1 atom and crosses represent electrons from the other atom. Square brackets and a charge (e.g. 2+) represent ions

cations

atoms with less electrons than protons

anions

negative ions. atoms with more electrons than protons

noble gases

positive ion. Group 0 elements. They already have a full outer shell. They are unreactive and don't normally form ionic bonds with other elements.

properties of ionic compounds

.only conducts electricity when molten or dissolved (cannot conduct as a solid)

.high melting points

identifying ionic compounds

An ionic compound formula has no overall charge.

naming ionic compounds

.Ionic compounds made from 2 different elements end in -ide.

.Ionic compounds made from 3 or more different elements end in -ate.

ionic compounds

ionic compounds form when millions of metal atoms transfer their outer electrons to millions of non-metals at the same time. The resulting oppositely charged ions are held together in ionic lattices

ionic lattices

ionic lattices are giant structures ( a regular repeating arrangement) that are held together electrostatic forces between positive and negative ions.

valence electrons

What you call electrons that are on the outermost shell.

empirical formulae

the simplest ratio of ions possible. eg 1calcium 2 bromides is CaBr₂

covalently bonded substances (examples)

water, polyester, diamond

Intramolecular bonds

forces between molecules; covalent bonds. They are strong

intermolecular forces

the force that holds together small molecules. They are weak.

small covalent molecules

Small molecules bonded together by intramolecular bonds called covalent bonds and held together by weak intermolecular forces.But they are weak and easy to break which means they have low boiling and melting point. They are often liquids and gases at room temperature.

Intermolecular Forces and Molecule Structure

The size of a molecule affects the overall strength of intermolecular forces. The strength of intermolecular forces affects the properties of a molecule.

properties of small covalent structure

It is usually gas or liquid at room temperature.

It has a low boiling and melting point

weak intermolecular bonds

they don’t conduct electricity because they have no delocalised electron.

properties of giant covalent structures

.They have very high melting and boiling points

.They have no specific empirical formula.

.No intermolecular force because they exist as 1 large molecule

polymers

.large, chain-like molecules made up of repeating units that can extend for thousands of atoms. They are held together by Strong covalent bonds between atoms in molecules and Weak intermolecular forces between molecules. Because of the large size of polymer molecules, the intermolecular forces add up to be quite strong.

Properties of polymers

.They are usually solid when at room temperature

.They melt easily as the intermolecular forces remain less strong than chemical bonds but add up to be quite strong due to the large size.

addition polymerisation

a process in which monomers, which are small organic molecules, are chemically bonded together to form a polymer, which is a long chain of repeating units.

diamond

A giant covalent structure which is an allotrope (form) of carbon.

allotrope

The existence of a chemical element in two or more forms

properties of diamond

.High melting point

.It is hard-lots of strong covalent bonds

.does not conduct electricity because there are no delocalised electrons in the structure.

Graphite

Graphite is an allotrope (form) of carbon.

properties of graphite

.it is soft-form layers of hexagonal (6-sided) rings, with weak intermolecular forces keeping the layers together. The layers can easily slide over one another

.conducts electricity

uses of graphite

graphene

graphene is an allotrope form of carbon.

properties of graphene

.It conducts electricity

.It is light but strong (a single layer of graphite)

uses of graphene

Its used in electronics (batteries, solar panels, phone screens). It makes them stronger while not making them heavier.

fullerenes

Fullerenes are molecules of carbon atoms that take up hollow structures. Their structure is usually carbon atoms arranged in hexagonal (6-sided) rings, but pentagonal (5-sided) and heptagonal (7-sided) carbon rings can also be found.

Buckminsterfullerene

A spherical fullerene. It was the first to fullerene that was discovered and its formula is C₆₀. It is technically a simple molecule because of its fixed size.

Uses of Buckministerfullerenes

It can be used as Catalysts, Lubricants ,As vehicles for transporting drugs into our bodies.

cylindrical fullerenes

Carbon nanotubes which are often called molecular wires because they have a tiny diameter but can be incredibly long.

Uses of cylindrical fullerenes

The strength and electrical conductivity of nanotubes make them useful In electronics, in nanotechnology and For strengthening materials (e.g. tennis racket frames).

metallic bonding

Metallic bonds are the electrostatic attraction between positive ions and negative delocalised electrons. The structure is a regular lattice of positive ions (cations) in a ‘sea’ of delocalised electrons.

delocalised electrons

Delocalised electrons are not bound to an atom and are free to move around within the lattice. Delocalisation happens because metal atoms have a small number of electrons in their outer shells.

pure metals

Metals that have giant structures with strong electrostatic forces between positive ions and delocalised electrons. All of the ions are the same size and these ions are arranged in layers.

properties of pure metals

.High melting and boiling points

.soft and malleable because ions are arranged in layers

alloys

A combination of 2+ elements, where at least 1 is a metal.The ions of the different elements are different sizes.

Why alloys are harder than pure metals

The ions are different sizes, distorting the regular layer, making it harder for layers to slide unlike pure metals which is why they’re in construction.

why metals are great conductors of heat and electricity

Metals conduct heat and electricity well. This is because the delocalised electrons that are around the layers of positive ions can carry a charge through the structure. The electrons move from the negative terminal to the positive terminal.