Atoms and Elements PDF

Learning Outcomes Understand and be able to define the chemical terminology: element, atom group, period, allotrope, ion, cation, anion. Name the subatomic particles comprising an atom, be aware of their charges and relative mass values. Be able to calculate the number of each type of su...

Learning Outcomes Understand and be able to define the chemical terminology: element, atom group, period, allotrope, ion, cation, anion. Name the subatomic particles comprising an atom, be aware of their charges and relative mass values. Be able to calculate the number of each type of subatomic particles in an element and ion from information derived from the periodic table. Identify and name the four types of atomic orbital Use the Pauli Exclusion Principle and the Aufbau principle to determine the electronic configuration of important biological elements and ions.  The Chemical Elements Surrounded by many different materials. Scientific curiosity – what are all these different things made up of? Ancient Greeks – the 4 humours – fire, earth, air and water. Scientists – over hundreds of years realised that everything was made up of a large, but finite, number of different types of particle. The chemical elements  The Chemical Elements and Life Approximately 90 naturally occurring chemical elements 25 elements essential for human life. 11 elements absolutely vital for any type of life Hydrogen (H), Oxygen (O), Carbon (C) and Nitrogen (N) are the key elements 99% of all of the atoms from which the body is formed are H, O, C and N.  Okay…but what is an element An element is a simple substance which cannot be broken down into a simpler form by CHEMICAL means. Carbon is an element – it cannot be broken down into anything else. Water has a CHEMICAL FORMULA of H2O. vs. Not a chemical element – but a chemical COMPOUND. Elements joined together by CHEMICAL BONDS. Can be broken down into the elements Hydrogen (H) and Oxygen (O)  Quick Test of Understanding Group the following into 2 categories – Na O2 elements or compounds. H 2S N Use the periodic table to help you. H Cl2 Discuss with your Xe friends.  Organising the elements The Periodic Table Best place to look for information on an element is the periodic table. Organised by Russian scientist Dmitri Mendeleev in 1869 Horizontal rows = periods. Regular pattern of change across periods with regards to physical and chemical properties. Vertical rows = groups Groups contain elements with similar physical and chemical properties. https://www.rsc.org/periodic-table/hist ory/about The Periodic Table  Atoms An atom is the smallest particle into which an element can be divided whilst still retaining the properties of the element. Carbon – diamonds - graphite - buckminsterfullerene All made up of 100% C atoms – just connected in slightly different ways by chemical bonds Allotropes What makes up an atom? Electrons inhabit Atoms are as small as we can go for elements the energy They are made up of three types of subatomic particles orbitals of an atom Protons (Positively [+1] Charged) Mass = 1 Neutrons (0 Charge) Mass = 1 Electrons (Negatively [-1] Charged) Protons Mass = approximately zero (red) & Neutrons Differences in the numbers of protons (blue) neutrons and electrons = different make up elements. the nucleus of an  Electronic Charges Atoms of elements can become electronically charged This happens when the atom loses or gains an electron Atom loses an electron, becomes positively charged: cation e.g. Na+ Atom gains an electron, becomes negatively charged: anion e.g. Cl – Some atoms will gain or lose more than one electron e.g Ca 2+, O 2- Atoms will gain and lose electrons to increase their energetic stability. Move from being high energy to being low energy – chemicals are generally happier being in the lowest energy state possible…this is why chemical reactions occur.  Using the periodic table to work out how many protons, neutrons and electrons. Atomic Number (Z) Number of Protons 26 Fe Relative Atomic Mass Number of Iron Protons + Neutrons 56 For an uncharged or NEUTRAL element the number of protons = number of ele  Your turn… Calculate the number of protons, neutrons and electrons in these biologically important elements and ions. Use your periodic table! C O 2- K + N Fe 2+ Cl - Fe 3+ H +  Atomic Orbitals The Bohr model of an atom – with electrons floating around a nucleus is a little outdated. Heisenberg and Schrodinger came up with the quantum model of atomic orbitals. Electrons occupy orbitals in different principal energy levels (given the symbol n and a number e.g. n = 1) Principal energy levels also called shells or electron shells. 4 types – called s, p, d & f Video on atomic orbitals  Atomic Orbital Energies I 8 O n Oxygen Each orbital can hold 2 electrons (maximum) – Pauli Exclusion c 16 Principle r e 3d 2 electrons in the same orbital will a have opposite spin s 4s i The lower energy orbitals must be n 3p filled before higher energy g orbitals – Aufbau Principle. 3s Degenerate orbitals must have electrons evenly distributed E 2p across them. n e 2s Gives rise to the electronic r configuration of an element g 1s i e Electronic Configuration = 1s 2s 2p 2 2 4  Hund’s Rule: Every orbital in a subshell is singly occupied with one electron before any one orbital is doubly filled S = 2 electrons; p = 6 electrons; d = 10 electrons; f = 14 pelectrons d f  Your turn… What are the electronic configurations of the following biologically important elements. C O 2- N Cl - H +  Reading and other Resources Essential Reading Chemistry for the Biosciences by Jonathan Crowe and Tony Bradshaw Chapter 2: Atoms the foundation of life. Recommended Video An alternative way t o get electronic conf iguration