2.  Atoms are made up of three types of smaller particles, namely protons, neutrons and electrons. These particles are known as subatomic particles. SUBATOMIC PARTICLE SYMBOLRELATIVE MASSRELATIVE ELECTRIC CHARGE PROTONP1+1 NEUTRONn10 ELECTRONe0 (almost)

3.  Protons and neutrons are found in the nucleus of an atom while electrons surround the nucleus.

4.  Each element is given a name and a symbol. Some examples of elements and their symbols are shown below. ELEMENTSYMBOLELEMENTSYMBOL HydrogenHSodiumNa HeliumHeMagnesiumMg LithiumLiAluminiumAl BerylliumBeSiliconSi BoronBPhosphorusP CarbonCSulphurS NitrogenNChlorineCl

5. Proton number Nucleon number

7.  Proton number = An elements is the number of protons in its atom.  Since atoms are neutral, the proton number is also the number of electrons in the atom.  Each elements has its own proton number. Proton number = electron number

8.  The nucleon number is also known as the mass number.  The relative mass of an atom is almost the same as its nucleon number.  Protons and neutrons are collectively called nucleons because protons and neutrons occupy the nucleus.

9.  Nucleon number: total number of protons and total number of neutrons in its atom.  From definition, or Nucleon number = number of proton + number of neutrons Number of neutrons = nucleon number – number of proton

10.  Isotopes are atoms of the same element with the same number of protons but different numbers of neutrons.  Isotopes of an element have the same: (a) number of protons in an atom. (b) number of electrons in an atom. (c) electron arrangement. (d) chemical properties because they have the same electron arrangement.

11.  Isotopes of an element have different: (a) nucleon number. (b) number of neutrons in an atom. (c) physical properties (such as density, melting point and boiling point), though these different are very small.  Eg: 3 He, 4 He, 12 C, 14 C, 235 U, and 239 U, respectively)

12. Element Number of Protons Number of Neutrons Number of Electrons Atomic Mass Atomic Number lithium carbon chlorine silver lead calcium Atomic Structure Worksheet Fill in the blanks for the elements in this chart. For the purposes of this chart, round all atomic masses to the nearest whole number.

13. Element Number of Protons Number of Neutrons Number of Electrons Atomic Mass Atomic Number lithium34373 carbon666126 chlorine1718173517 silver47614710847 lead821258220782 calcium20 4020 ANSWER

15.  The electron configuration (electron arrangement) of an atom is the arrangement of electrons in shells (orbits) around the atom's nucleus.

16.  Example SODIUM Proton number = 11 Electron number = 11 Electron configuration = 2.8.1

17.  The electrons in the last shell of an atom are known as valence electrons. They determine the chemical properties of the element. Electron configuration = 2.7 Valence electron = 7 Electron configuration = 2.4 Valence electron = 4 Electron configuration = 2.8.4 Valence electron = 4

18.  Helium has a complete shell of 2 valence electrons or duplet condition.  Similarly, neon and argon also have 8 valence electrons or the octet condition.  These elements are monoatomic and are very stable gases. Helium 2 Neon 2.8 Argon 2.8.8

19.  Number of shells = Period in Periodic Table  Valence electron (1 and 2) = Group in Periodic Table  Valence electron (3 – 8) = Valence electron + 10 = Group in P.Table eg: Valence electron =7 So, Group 17 2 8 1 SODIUM Proton number = 11 Electron number = 11 Electron configuration = 2.8.1 Position in Periodic Table Period: 3 Group : 1

20. ElementProton number Number of electrons Number of elements in shellElectron arrangement Number of valance electrons 1234 Oxygen8826 2.66 Fluorine9927 2.77 Neon10 28 2.88 Sodium11 281 2.8.11 Magnesium12 282 2.8.22 Aluminium13 283 2.8.33 Silicon14 284 2.8.44

21. 1. Draw electron arrangement for element Na, Ar, Mg, Al, Cl, O, C, N. 2. State the valence electron for each elements 3. State the position in Periodic Table