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ATOMIC STRUCTURE What makes atoms of different different from each other? Name ____________________________ Class __________ Date __________ Teacher ____________________________ CHEM - ADDITIONAL BOOKLET 1 1 elements ATOMIC STRUCTURE You should: Tick Know that the relative masses of protons, neutrons and electrons and their relative electric charges are shown: Proton : mass 1 : charge +1 Neutron : mass 1 : charge 0 Electron : mass negligible : charge -1 Understand that the atom as a whole has no electrical charge because the number of electrons in the orbits (shells) is equal to the number of protons in the nucleus. Know that all atoms of a particular element have the same number of protons and atoms of different elements have different numbers of protons. Understand the terms atomic number and mass number Use data given in the form 23 Na 11 to give the number of protons, neutrons and electrons present in the atom. 2 SUMMARY SHEETS The atom at G.C.S.E This is a three dimensional depiction of the atom CARBON A two dimensional depiction of an atom of CARBON When we draw atoms at G.C.S.E level we draw them as two dimensional pictures. From the above diagram you can see that at the centre of the atom there are tiny particles called PROTONS. PROTONS are POSITIVE and have a mass of 1 ATOMIC MASS UNIT (a.m.u). PROTONS are given the symbol p+ The NUMBER of PROTONS in the NUCLEUS of an atom give that atom its IDENTITY. The NUMBER of PROTONS in the NUCLEUS is given by the ATOMIC NUMBER. The atomic number for each element can be found in the PERIODIC TABLE. 3 ELECTRONS ELECTRONS are NEGATIVE and are given the symbol e-. Electrons are so small; we say that their mass is NEGLIGABLE. The NUMBER of electrons is also given by the ATOMIC NUMBER. Electrons DO NOT give atoms their identity. The number of electrons can CHANGE so that ATOMS become IONS. In a NEUTRAL ATOM the NUMBER OF ELECTRONS is always the SAME as the NUMBER OF PROTONS. Electrons orbit the nucleus of an atom in shells (sometimes known as orbits or energy levels). Putting electrons into their shells There are many shells around the nucleus of an atom. The inside shell can hold TWO electrons. The next three shells hold EIGHT electrons. Electrons fill shells from the inside out. A new shell cannot be started until its inner shell is FULL. 4 NEUTRONS Neutrons have a mass of 1 ATOMIC MASS UNIT a.m.u. The same mass as the protons. Neutrons have NO OVERALL CHARGE they are said to be NEUTRAL. Neutrons exist alongside protons in the NUCLEUS of an atom. The number of neutrons can be found by taking the ATOMIC NUMBER away from the MASS NUMBER. The MASS NUMBER is the mass of an atom which is the same as the TOTAL number of protons AND neutrons as they all weigh 1 a.m.u. This information for fluorine tells us the mass and atomic number for one of its atoms. ELEMENTS Atoms in a particular element are identical as they all contain the same number of PROTONS. For example carbon is carbon because its atoms contain 6 protons. If the atoms contained 7 protons the element would be nitrogen. It’s the protons not the neutrons or electrons that tell us what element an atom is part of. 5 VALENCY Many atoms react with others in order to ensure their outer shells become full. This will make the atom more stable. Atoms can achieve full outer shells by LOSING, GAINING or SHARING electrons. The NUMBER of electrons lost, gained or shared is called the VALENCY. END OF SUMMARY SHEETS Key skill communication KEY WORDS Read the summary sheets above and write down as much information as you can about the following key words. Use examples and diagrams where possible. Word/phrase Information Atom Use sodium as an example. Draw an atom of sodium with its protons, neutrons and electrons. 6 Atomic number Again, use sodium as an example. Explain what information the atomic number for sodium gives us. Mass number Sodium again! Proton Give general information about a proton here. For example, where it is found, what its mass is, what its charge is. Explain how to use atomic numbers to find out the number of protons. Neutron Give general information about a neutron here. For example, where it is found, what its mass is, what its charge is. Explain how to use mass and atomic numbers to find out the number of neutrons. 7 Electron Give general information about an electron here. For example, where it is found, what its mass is, what its charge is. Explain how to use atomic numbers to find out the number of electrons. Electronic Structure Use sodium or any other element here to talk about electronic structure which is the way in which electrons are arranged in their shells. Valency Write out the electronic structures for sodium, magnesium, oxygen , chlorine and neon and work out what their valencies are. The valency is the number of electrons they each need to lose, gain or share to gain a full outer shell. If they already have a full outer shell then their valency is zero. NOW FILL IN THE FOLLOWING TABLE. Draw the electrons as crosses. Draw the nucleus as a black spot but label the correct number of protons and neutrons that would be within it. Look up the periodic table for the atomic/mass numbers! 8 symbol At Mass n.o n.o H 1 He 2 Li Electron arrangement Valency of atom 1 1 7 Be B 9 Picture of atom C 6 N 7 O F 9 Ne Na 0 11 2:8:1 1 10 Mg Al 13 Si P S 15 16 31 2:8:6 2 11 Cl Ar K Ca 20 12 Key Words Atom the smallest part of a substance that cannot be split into anything simpler. Element an element is made up of atoms that are all identical as they each contain the same number of protons. Protons positive sub-atomic particles that exist in the nucleus of an atom. Neutrons neutral sub-atomic particles that exist in the nucleus of an atom. Electrons negative sub-atomic particles that exist in shells/energy levels that surround the nucleus of an atom. Mass n.o the mass of a single atom which is due to the total number of protons and neutrons it contains. Atomic n.o the total number of protons in an atom. This in turn is the same as the number of electrons in a neutral atom (very often electrons are lost or gained forming ions) 13