Year 11 Intensive Study Day Atomic structure and bonding

Atomic structure and bonding learning outcomes – I will be able to: Recall that atoms are made up of smaller particles Remember the names and locations of these particles in the atom Recall the relative masses and charges of protons, neutrons and electrons Understand that each element has atoms with a particular atomic number Use a periodic table to work out the number of neutrons in an atom from the atomic number and mass number Explain what isotopes are Show that non-metals form covalent bonds by sharing electrons

Atoms – the building blocks All substances are made from very tiny particles called atoms. John Dalton had ideas about the existence of atoms about 200 years ago but only recently have special microscopes been invented that can “see” them. Water

Elements – different types of atom Elements are the simplest substances. There are about 100 different elements. Two of John Daltons ideas were: –Elements contain different types of atom. –Each element has only one type of atom. N S O C Fe K

Atoms – How Small? small.Atoms are about 1/100,000,000 cm across. They are small. To make an atom the size of a football we would have to magnify it to around 3,000,000,000 times its normal size If we magnified the size of a football by the same amount it would stretch from the UK to the USA! N X 3,000,000,000

Atoms – How Heavy? A single grain of sand contains billions of atoms of silicon and oxygen. It follows that each atom must have an extremely small mass. However, it is still possible to find out the relative masses of atoms. Si O Billions of these atoms join to form each tiny grain of sand O

The Atom: Check It Out! From memory, draw a labelled diagram of the atom showing the nucleus and label the protons, neutrons and electrons

Properties of Sub-atomic Particles There are two properties of sub-atomic particles that are especially important: –Mass –Electrical charge ParticleCharge Relative Mass Protons+11 Neutrons01 Electrons Element atoms contain equal numbers of protons and electrons and so have no overall charge

Atomic Number alwaysThe atom of any particular element always contains the same number of protons. E.g. –Hydrogen atoms always contain 1 proton –Carbon atoms always contain 6 protons –Magnesium atoms always contain 12 protons The number of protons in an atom is known as its atomic number. It is the smaller of two numbers shown in most periodic tables 12 C 6

How Many Protons? Here is some data about elements taken from the Periodic Table. What is the atomic number of the elements? 23 Na Fe Sn F 9 27 Al Activity

Mass Number Calculate the mass number of the atoms shown. AtomProtonsNeutronsMass Number Helium22 Copper2935 Cobalt2732 Iodine5374 Germanium MASS NUMBER = Number of protons + number of neutrons Activity

How Many Neutrons Calculate the number of neutrons in these atoms. AtomMass Number Atomic Number Number of Neutrons Helium42 Fluorine199 Strontium8838 Zirconium9140 Uranium23892 Number of Neutrons = mass number - atomic number Activity

How Many Electrons Fill in the blank columns AtomProtonsNeutronsElectronsAtomic number Mass Number Boron56 Potassium1920 Chromium2428 Mercury80121 Argon Note – atomic number is defined as the number of protons rather than electrons because atoms can lose (or gain) electrons but do not normally lose protons Activity

RAM Challenge!! Have a go at completing the RAM challenge – you have 10 minutes to use the information given to work out the missing numbers of protons, electrons and neutrons!

Working Out Electron Arrangements Remember opposites attract so if.. protons are + and electrons are charged, electrons will occupy the shells nearest the nucleus unless these shells are already full. 1.How many electrons do the element atoms have? (This will equal the atomic number). 2.Keeping track of the total used, feed them into the shells working outwards until you have used them all up. 1st Shell: Fills this first 2 nd Shell: Fill this next Drawing neat diagrams helps you keep track!

The Electrons in Carbon

Challenge! Using the last example to help you, can you complete the next couple of diagram to show their electron arrangements?!

Activity Drag the words at the top to their correct places in the sentences

Types of bonding Atoms can be joined together in 3 possible ways All three types involve changes in the electrons in the outermost electron shells of the atoms Ionic Bonding Metal and non-metal Covalent Bonding Non-metals only Metallic Bonding Metals only

Now lets look at a summary of covalent bonding

Covalent compounds Covalent compounds are formed when non-metal atoms react together. As these atoms come near their outer electrons are attracted to the nucleus of both atoms and become shared by the atoms. The shared electrons count towards the shells of both atoms and therefore help fill up incomplete electron shells.

Covalent bonds Covalent compounds are held together by this sharing of electrons. covalent bond.A pair of electrons shared in this way is known as a covalent bond. It is sometimes represented in full bonding diagrams (see figure 1). Often these bonds are just shown as a pair of electrons (xx) or even just a line (see figure 2). F XXXX F F F - Figure 1Figure 2

Now lets look at a summary of ionic bonding

Most ionic compounds contain a metal and a non-metal. When metals react they lose outer shell electrons to leave a full electron shell. This produces a charged atom (ion) with a + charge. Lose 1 or more electrons Neutral atom n+n+ Positive ion When non-metals react with a metal they gain electrons to achieve a full electron shell. Gain 1 or more electrons Neutral atom n-n- Negative ion IONIC BONDING

Ions and electron structures Metals lose electrons to form positive(+) ions called cations. Non-metals gain electrons to form negative (–) ions called anions. n+n+ n-n- We know that the atoms lose or gain electrons to achieve full electron shells. To understand more about how ionic compounds form we must look at what is happening to the outer shell electrons.

Formation of sodium chloride 1. Formation of sodium ions Sodium has 1 electron in its outer shell. If it loses this it will have no partially filled shells. Loses 1 electron Sodium 1+ ion (2.8.0) Sodium atom (2.8.1) This only happens if there is another atom able to accommodate the lost electron. Na Na+

Formation of sodium chloride 2.Formation of Chloride ions Chlorine has 7 electrons in its outer shell. If it gains 1 electron it can achieve a full outer electron shell. It is, therefore, going to be able to accept the electron that the sodium wants to lose. Chlorine atom (2.8.7) Gains 1 electron (from sodium) Chlorine I - ion (2.8.8) Cl

Simpler electron diagrams We can assume full inner electron shells. We can therefore sometimes shorten bonding diagrams by omitting to draw the inner electron shells. Na Cl Na Cl