Can you recall… What is Matter? Matter is anything that has mass and takes up space.

What is matter made of?

Democritus “…if one were to break up matter into smaller and smaller piece, there would come a point when it could no longer be divided further.” He called this smallest indivisible bit of matter ‘atom’ (from the Greek word atomos which means indivisible). Greek Philosopher (460 B.C. – 370 B.C.)

Particles that make up of matter Using a Scanning Tunneling Microscope (STM), scientists are now able to observes the particles that make up matter. Gold atoms Scanning Tunneling Microscope

Particles that make up of matter Iron on Copper

What is an atom? An atom is the smallest unit of an element, having the properties of that element. Atom! solid liquid gas

Given that… an atom is the smallest unit of an element, having the properties of that element… Question for thought: Is a copper atom identical to a zinc atom?

Let’s learn more about the ATOM

With nothing else inside? Model of an Atom Are atoms like solid balls? With nothing else inside?

The Changing Model of the Atom The history of atom: Dalton model (Billiard Ball Model) Thomson model (Plum Pudding Model) Lewis model (Cubical Atom Model) Nagaoka model (Saturnian Model) Rutherford model (Planetary Model) Bohr model (Rutherford–Bohr Model) Bohr–Sommerfeld model (Refined Bohr Model) Gryziński model (Free-fall Model) Schrodinger model (Electron Cloud Model)

The Ever Changing Model… Psy, psy, psy, psy, psy… (Which model should I learn?)

Presenting to you… electron proton neutron nucleus The Bohr Model

Particles smaller than an atom… Note: The nucleus consists of protons and neutrons Nucleus is positively charged. Why? Electrons move around very rapidly. They tend to occupy layers or shells at different distances from the nucleus. Atoms - made up of subatomic particles positively charged proton nucleus neutron neutral shell negatively charged electron

Subatomic Particles proton nucleus neutron electron positively charged Symbol Relative Mass Charge Proton p 1 1+ Neutron n Electron e- 1/1836 1- neutral electron negatively charged

Thinking Time… Particle Symbol Relative Mass Charge Proton p 1 1+ Neutron n Electron e- 1/1836 1- Why is the term "relative mass" used rather than just mass?

Thinking Time… Hints… Mass of proton ≈ 1.67×10−27 kg Mass of neutron ≈ 1.67×10−27 kg Mass of electron ≈ 9.11×10−31 kg

Thinking Time… Mass of proton, neutron and electron are too small and inconvenient to work with. By using relative mass, we do not have to remember the exact value of the various masses.

Moving on… The Periodic Table

The Periodic Table

Counting protons… Proton Number The number of protons in an atom is called the proton number. Proton number is also known as the Atomic Number. From Periodic Table…

Counting protons & neutrons… Nucleon Number Nucleon number is the number of protons and neutrons in the nucleus of an atom. Nucleon number is also called the Mass Number.

Nucleon Number Nucleon (Mass) number = number of protons + number of neutrons

Carbon atom in symbol form: C. Can also be written as carbon-12. 6

Question How many protons, electrons, and neutrons are there in a C atom? 6 protons, 6 electrons and 6 neutrons.

Thinking Time… What is the proton number and nucleon number of an atom of Cu? Proton number: 29  Nucleon number: 64

Thinking Time… What is the atomic number and mass number of an atom of Ca? Atomic number: 20  Mass number: 40

Thinking Time… Using the periodic table, identify the mass number of an atom of bromine (b) the atomic number of an atom of boron (c) the proton number of an atom of platinum (d) the nucleon number of an atom of niobium

Thinking Time… Using the periodic table, identify the mass number of an atom of bromine - 80 (b) the atomic number of an atom of boron - 5 (c) the proton number of an atom of platinum - 78  (d) the nucleon number of an atom of niobium - 93

Complete the table: Element H Na S Number of protons Number of electrons Number of neutrons

Complete the table: Element H Na S Number of protons 1 11 16 Number of electrons Number of neutrons 12

Back to the Atomic Model… The centre of an atom is called the nucleus which contains the protons and neutrons. protons nucleus neutrons

The Atomic Model… The electrons in an atom are arranged in shells (orbits) at different distances from the nucleus. Note: Shells are also called energy levels. protons neutrons nucleus 1st shell 2nd shell 3rd shell 4th shell electron

The Atomic Model Each shell can hold a certain maximum number of electrons. (a) 1st shell - 2 electrons (b) 2nd shell - 8 electrons (c) 3rd shell - 8 electrons (1st 20 elements only) Advanced: For elements after calcium in the 4th period, their third shell can hold up to 18 electrons. 1st shell 2nd shell electron 3rd shell 4th shell

Question An atom can be described as an electrically neutral entity made up of a positively charged nucleus at its centre with negatively charged electrons moving around the nucleus.

Question An atom can be described as an electrically neutral entity made up of a positively charged nucleus at its centre with negatively charged electrons moving around the nucleus. (a) Why is the atom electrically neutral? Number of electrons = number of protons. Equal positive and negative charges (b) Why is the nucleus positively charged? The nucleus contains protons and neutrons. Protons are positively charged while neutrons are electrically neutral.

Differentiating different elements How do I differentiate the atoms of one element from the atoms of another element? All atoms of the same element have the same number of protons while those of different elements contain different number of protons. 12 23 C vs Na 6 11

What are Isotopes? Isotopes are atoms of the same element with different numbers of neutrons. -> same proton number, different nucleon number E.g. carbon has 3 isotopes: 12 6 C 13 6 C 14 6 C

Drawing the full electronic configuration Electron Arrangement Nitrogen-14 atom has 7 electrons Key - electron p - proton n - neutron 7 p 7 n Drawing the full electronic configuration Note: full electronic configuration of an atom shows the arrangement of electrons in different shells.

Writing the electronic configuration: 2.5 Electron Arrangement Nitrogen-14 atom has 7 electrons Key - electron p - proton n - neutron 7 p 7 n shows arrangement of electrons in different shells. Writing the electronic configuration: 2.5 1st shell 2nd shell separate the 2 shells

Electron Arrangement Argon-40 atom has 18 electrons Key - electron p - proton n - neutron 18 p 22 n electronic configuration of 2.8.8

Valence Shell Valence shell - farthest occupied shell from the nucleus Valence electron - electron in the valence shell 7 p 7 n

Valence Shell Note: only valence electrons are involved in chemical reactions. 7 p 7 n

Outer electronic structure only valence electrons are drawn 7 p 7 n Key - electron p - proton n - neutron

Formation of Ions During chemical reactions, some atoms might lose/gain electron(s). Atom becomes an ion (charged particle) when it gains or loses electron(s).

Question Why does an atom become a charged particle when it gains or loses electron(s)? An atom is electrically neutral because number of electrons = number of protons (equal positive and negative charges). When it gains or loses electron(s), the positive and negative charges are not balanced. Therefore, the atom becomes a charged particle.

Formation of cations When an atom loses one or more electrons, it becomes a positively charged particle called cation. Lithium atom (Li) 3 electrons 3 protons Net charge: 0 Lithium ion (Li+) 2 electrons 3 protons Net charge: +1

Formation of anions When an atom gains one or more electrons, it becomes a negatively charged particle called anion. Fluorine atom (F) 9 electrons 9 protons Net charge: 0 Fluoride ion (F-) 10 electrons 9 protons Net charge: -1

Question for Thought Why do atoms become ions? To obtain a full valence shell To obtain the same electronic structure of a noble gas so as to be stable. (Note: this will be covered under Chemical Bonding)

Fill up the blanks… Charge of ion Element Name of ion Symbol of ion No. of electron gained No. of electron lost Oxygen Sulfur Oxide Sulfide O2- S2- Fluorine Chlorine Fluoride Chloride F- Cl- Hydrogen Lithium Sodium Potassium H+ Li+ Na+ K+ Beryllium Magnesium Calcium Copper Iron Copper (II) Iron (II) Be2+ Mg2+ Ca2+ Cu2+ Fe2+ Aluminium Iron (III) Al3+ Fe3+

Fill up the blanks… Charge of ion Element Name of ion Symbol of ion No. of electron gained No. of electron lost -2 Oxygen Sulfur Oxide Sulfide O2- S2- 2 -1 Fluorine Chlorine Fluoride Chloride F- Cl- 1 +1 Hydrogen Lithium Sodium Potassium H+ Li+ Na+ K+ +2 Beryllium Magnesium Calcium Copper Iron Copper (II) Iron (II) Be2+ Mg2+ Ca2+ Cu2+ Fe2+ +3 Aluminium Iron (III) Al3+ Fe3+ 3

Questions… Do metals generally form cations or anions? cations Do non-metals generally form cations or anions? anions

The Periodic Table Scientists have classified all discovered elements into a chart called the Periodic Table

The Periodic Table In the Periodic Table, elements are arranged in order of increasing proton (atomic) number and are classified according to Groups and Periods.

Vertical Row: Group Elements in the same group have similar chemical properties and will undergo the same type of chemical reactions

Horizontal Row: Period As you move across a period, the properties of the elements will change gradually from metallic to non-metallic

Group Groups are numbered from I to VII and then 0

Group Alkali metals Noble gases Alkaline earth metals Halogens Transition metals

Group Elements in the same group have similar chemical properties and will undergo the same type of chemical reactions.

Elements in the Periodic Table Li Na K Rb Cs Fr Group I – Alkali Metals Lithium, Sodium, Potassium, Rubidium, Cesium, Francium. Metals and solid at room temperature. Very reactive.

Elements in the Periodic Table Be Mg Ca Sr Ba Ra Group II – Alkaline Earth Metals Beryllium, Magnesium, Calcium, Strontium, Barium, Radium.

Elements in the Periodic Table Al Ga In Tl Group III Boron, Aluminum, Gallium, Indium, Thallium Except B, Group III elements are all metals. B is a metalloid.

Elements in the Periodic Table Ge Sn Pb Group IV Carbon, Silicon, Germanium, Tin, Lead Carbon is a non-metal. Si and Ge are metalloids. Sn and Pb are metals. A metalloid is an element that has some of the physical characteristics of a metal but some of the chemical characteristics of a non-metal.

Elements in the Periodic Table As Sb Bi Group V Nitrogen, Phosphorus, Arsenic, Antimony, Bismuth. Non-metals (N, P) to metalloids (As, Sb) to metals (Bi).

Elements in the Periodic Table Se Te Po Group VI Oxygen, Sulfur, Selenium, Tellurium, Polonium. Non-metals (O, S, Se) to metalloids (Te) to metals (Po).

Elements in the Periodic Table F Cl Br I At Group VII – the Halogens Fluorine, Chlorine, Bromine, Iodine, Astatine. All non-metals.

Elements in the Periodic Table Ne Ar Kr X Rn Group 0 – the Noble Gases Helium, Neon, Argon, Krypton, Xenon, Radon. Least reactive elements. Also known as inert gases, or rare gases.

Elements in the Periodic Table The Transition Elements All metals Au Hg Pt Fe Cu Ti Rh Mn Zr V Cr Ni Zn Ag

Period 1st period 1st shell fully occupied 2nd period 2nd shell fully occupied 3rd period

Electronic configuration Fill up the blanks. Element Proton number Number of electrons in Electronic configuration Period Group 1st shell 2nd shell 3rd shell 4th shell H 1 He 2 Li 3 Be 4 B 5 C 6 N 7 O 8 F 9 Ne 10 Na 11 Mg 12 Al 13 Si 14 P 15 S 16 Cl 17 Ar 18 K 19 Ca 20

Electronic configuration Fill up the blanks. Element Proton number Number of electrons in Electronic configuration Period Group 1st shell 2nd shell 3rd shell 4th shell H 1 - He 2 Li 3 2.1 I Be 4 2.2 II B 5 2.3 III C 6 2.4 IV N 7 2.5 V O 8 2.6 VI F 9 2.7 VII Ne 10 2.8 Na 11 2.8.1 Mg 12 2.8.2 Al 13 2.8.3 Si 14 2.8.4 P 15 2.8.5 S 16 2.8.6 Cl 17 2.8.7 Ar 18 2.8.8 K 19 2.8.8.1 Ca 20 2.8.8.2

number of valence electrons for each element = group number

elements in the same group have similar chemical properties Group I 1 valence e- Electronic configuration – 2.1 elements with similar electronic configurations have similar chemical properties elements in the same group have similar chemical properties Electronic configuration – 2.8.1 Electronic configuration – 2.8.8.1

Group I Reactivity

Metals vs Non-metals Non-metals Metals 74

Non-metals Metals Across the period, the properties of elements change from metallic to non‐metallic.

Periodic Table: An organised table that consists of all the elements discovered. Non-metals Metals 76

Periodic Table: An organised table that consists of all the elements discovered. Non-metals Metals 77

Charges on ions Charges on the ions formed are related to the group number and number of valence electrons. Element Na Mg Al Si P S Cl Ar Group number I II III IV V VI VII Formula of ion Na+ Mg2+ Al3+ - P3- S2- Cl- e- gain/lost 1 2 3

Charges on ions Element Na Mg Al Si P S Cl Ar Group number I II III IV V VI VII Formula of ion Na+ Mg2+ Al3+ - P3- S2- Cl- e- gain/lost 1 2 3 Metal atoms lose their valence electrons to form cations with charges corresponding to their group number. Non-metal atoms gain electrons to form anions. The charges on the anions corresponding to the number of electrons gained to fill their valence shells with eight electrons.

Try this! Draw a labelled diagram to show the full electronic configuration in an atom of (i) S

Try this! Draw a labelled diagram to show the full electronic configuration in an atom of (ii) Ca