2024 Chemistry Main PPT PDF

CHEMISTRY THE STUDY OF MATTER  TOPIC OVERVIEW 01 02 03 04 05 Atomic Electronic Ionic Covalent Metallic Structure Configuration Bonding Bonding Bonding  RECAP Y8: ELEMENTS  Elements are substa...

CHEMISTRY THE STUDY OF MATTER  TOPIC OVERVIEW 01 02 03 04 05 Atomic Electronic Ionic Covalent Metallic Structure Configuration Bonding Bonding Bonding  RECAP Y8: ELEMENTS  Elements are substances made up of only one type of atom  There are 118 known elements on the periodic table  Each element is given a symbol that represents their name:  H for hydrogen  Pb for lead  RECAP Y8: ARRANGEMENT OF ATOMS Atoms can exist as either:  Single atoms  Molecules (groups of atoms)  Crystal lattices (grid-like structure) … and this year you will finally find out why! ATOMIC STRUCTURE  HISTORY OF THE ATOMIC MODEL John Dalton  Atoms are indivisible and indestructible  An element is made up of atoms that are identical in size, mass and other properties  Different elements had atoms of differing size and mass  ‘Bowling ball’ model  HISTORY OF THE ATOMIC MODEL JJ Thomson  Discovered the electron while working with cathode rays  Electrons are negatively charged and 2000 times lighter than the smallest known atom, the hydrogen atom  If atoms are neutral, then the negative electrons must be embedded in a ball of positive charge  “Plum pudding” model  HISTORY OF THE ATOMIC MODEL Ernest Rutherford  Discovered that atoms are mostly empty space with a small, positive nucleus  Negative electrons occupied this empty space  “Nuclear model”  HISTORY OF THE ATOMIC MODEL Niels Bohr  Refined Rutherford’s model by saying that electrons orbit around the nucleus along certain pathways  Like the solar system, where planets are held in orbit by the Sun’s gravity  But in the atom, negative electrons are held in orbit by the electrostatic attraction to the positive nucleus  “Planetary model” HISTORY OF THE ATOMIC MODEL  ATOMIC STRUCTURE  The atom is made of three subatomic particles: 1. Protons (+ charge) 2. Neutrons (neutral charge) 3. Electrons (- charge)  Protons and neutrons are found in the nucleus. They are relatively heavy.  Electrons orbit the nucleus. They are very light.  ATOMIC STRUCTURE What role do  protons,  neutrons and  electrons play in determining the  type,  mass,  stability and  charge of the atom?   What determines the type of atom? The number of protons  What determines the mass of an atom? THE ROLE OF PROTONS, The number of protons & neutrons NEUTRONS &  What determines the net charge of an atom? ELECTRONS The ratio of protons to electrons  What determines the stability of an atom? The ratio of neutrons to protons  ATOMIC STRUCTURE PROTON NEUTRON ELECTRON LOCATION MASS CHARGE ROLE  ATOMIC STRUCTURE PROTON NEUTRON ELECTRON LOCATION Nucleus Nucleus Orbits the nucleus MASS 1 1 Negligible (0.0005) CHARGE +1 0 -1 ROLE Determines the Required for Responsible for identity of atom stability of nucleus reactivity  ATOMIC STRUCTURE & THE PERIODIC TABLE The periodic table is organised to give us information about the Atomic number atomic structure of elements.  Atomic number = number of Symbol protons Name  Mass number = number of protons + neutrons But why does the mass number have decimals??? Mass number  ISOTOPES Isotopes are atoms of the same element (same number of protons) that have a different number of neutrons. E.g. the element Carbon has 3 known isotopes:  Carbon-12: 6 protons + 6 neutrons  Carbon-13: 6 protons + 7 neutrons  Carbon-14: 6 protons + 8 neutrons  ISOTOPES The mass number on the periodic table is a calculated average of all known isotopes of an element – that’s why it is not a whole number! 98.9% 1.1% 4 valence electrons, so both are unwilling to give away electrons 2. Instead, they ‘share’ a pair of electrons, forming a covalent bond 3. No electrons leave their original atoms, so the atoms remain neutral (no ions are formed) EXAMPLE: CHLORINE GAS  Chlorine gas is a covalent molecule – – with two chlorine atoms, Cl2 – – – – – – – – – – – –  A neutral chlorine atom has 17 – – Cl – – Cl – – electrons, arranged 2, 8, 7 – – – – – –  Each chlorine atom needs one – – – – – – more electron to achieve a full – – outer shell (2, 8, 8) EXAMPLE: CHLORINE GAS – – – – – –  To make it easier to visualise, – Cl Cl – we are only going to look at the valence shell – – – – – – EXAMPLE: CHLORINE GAS – –  Each atom will ‘share’ an electron, forming a pair – – of shared electrons – –  The pair of electrons is included in the outer shell – Cl Cl – of both atoms at once, giving both atoms a full – outer shell – – – – –  Both chlorine atoms are now covalently bonded by a single pair of shared electrons  EXAMPLE: CHLORINE GAS – – – – – – –  The chemical formula for a molecule chlorine gas Cl Cl – is Cl2 – two chlorine atoms bonded together – –  A single covalent bond (one pair of shared – – – – electrons) can be represented by a straight line between both atoms EXAMPLE: OXYGEN GAS –  A neutral oxygen atom has 8 electrons, – – – – – – – arranged 2, 6 – O O –  Each oxygen atom needs two more – – – – electron to achieve a full outer shell – – (2, 8) EXAMPLE: OXYGEN GAS – – – –  To make it easier to visualise, we are – O – O – only going to look at the valence – – – shell – – EXAMPLE: OXYGEN GAS  Each atom will ‘share’ two electrons, forming a two pairs of shared electrons – – – –  The pairs of electrons are included in the outer – – shell of both atoms at once, giving both atoms a full O – O outer shell –  Both oxygen atoms are now covalently bonded by – – – – two pairs of shared electrons EXAMPLE: OXYGEN GAS – – – – – –  The chemical formula for a molecule oxygen gas is O – O O2 – two oxygen atoms bonded together – – – – –  A double covalent bond (two pair of shared electrons) can be represented by a two straight lines between both atoms EXAMPLE: METHANE GAS A neutral carbon atom has 6 electrons, arranged 2, 4 –  Carbon needs four more electron – – to achieve 2, 8 – C – H A neutral hydrogen atom has 1 valence – – electron  Hydrogen needs one more electron In what ratio will these two elements react? to achieve 2 (first shell is full at 2 e -) EXAMPLE: METHANE GAS – H  To make it easier to visualise, we are – only going to look at the valence – – shell H – C – H  The ratio is one carbon : four hydrogen – – H EXAMPLE: METHANE GAS H  Carbon becomes the centre atom and will ‘share’ its electrons, forming a pair of shared electrons – – with each hydrogen atom – – H C H  Each hydrogen atom is now covalently bonded to – – the carbon atom by a single pair of shared – – electrons H EXAMPLE: METHANE GAS H – – – – H C H  The chemical formula of methane gas is CH 4 – –  Each covalent bond (one pair of shared electrons) – – can be represented by a straight line between H carbon and hydrogen  COVALENT BONDING – WATER Draw the number of valence Draw how electrons are shared in electrons for each element: this covalent compound: In what ratio will these O H elements react?  COVALENT BONDING – AMMONIA GAS Draw the number of valence Draw how electrons are shared in electrons for each element: this covalent compound: In what ratio will these N H elements react?  COVALENT BONDING – CARBON DIOXIDE Draw the number of valence Draw how electrons are shared in electrons for each element: this covalent compound: In what ratio will these C O elements react? METALLIC BONDING METALLIC BONDING Metallic bonding is a type of chemical bonding that takes place between two metals 1. Metal atoms usually have