1. Atom-Building blocks of matter What are the main
All matter is composed of extremely small particles called atoms.
Atoms of the given element are identical in size, mass and other properties
Atoms can not be subdivided, created or destroyed.
Atoms of different elements combine in simple whole number ratio.
In chemical reactions, atoms are combines, separated or rearranged

2. How does Dalton’s atomic theory support law of conservation of mass during chemical changes?
How do these chemical changes between carbon © and oxygen =(O) atoms account for law of conservation mass?
C OO OCO
1 ‘C’ ‘O’ atoms = 1 C + 2 ‘O’ atom
C O CO
1 C ‘O’ = C ‘O’ atom
# of atoms are same before and after chemical change. It is according to Dalton’s atomic theory

3. How does modern atomic theory differ from Dalton’s atomic theory?
Dalton’s atomic theory Modern atomic theory
Atoms are indivisible Atoms are divisible
Atoms of the same Atoms of the same element
Element are identical May be different (Isotopes)
Atoms can not be Atoms can be destroyed
Destroyed or created (Nuclear reaction) E = mc2

4. JJ Thomson

5. JJ Thomson Discovered electron is an essential particle of an atom in his cathode ray tube experiment. He suggested electron pudding model
Draw JJ Thomson’s electron pudding model of atom and make your decision and support if atom will be negatively charge, neutral or positively charge particle?

6. Cathode rays made with negatively charged particles

8. Thomson suggested for positive charge to make electrically neutral atom

9. What was the idea that lead to discovery of nucleus?
According to Rutherford’s gold foil experiment, draw the two parts of an atom and suggest why atom is a neutral particle?

10. Protons p +1 1 In side nucleus Electrons e -1 0 out side nucleus
What three subatomic particles of Atom their properties and their locations in an atom?
Name Symbol Charge Mass Location
Protons p In side nucleus
Electrons e out side nucleus
Neutrons n In side nucleus
Why an atom is neutral? # p = # e
# positive charge = # negative charges

11. Counting # subatomic particles
What is atomic Number? # protons in the nucleus is called atomic #
What is the importance of atomic number of an atom of an element?
The Atomic # determines the identity of an element ( Atomic # =11, it is sodium element)
What is mass Number of an atom?
Sum of # protons and # neutrons is called mass number (nucleons).
How will you calculate # neutrons in an atom if its atomic number and mass number are given?
Mass number – atomic number = number of neutrons

12. Nuclear atom

13. a) What are isotopes of an element
a) What are isotopes of an element? b) What are three isotopic symbols hydrogen atoms of protium (H), deuterium(D) and tritium(T)? C) How they are similar and different from each other?
Symbol Mass # Atomic number #P # e #n
Protium 11H
Deutrium H
Tritium H

14. Compare and contrast the two isotopes of chlorine (3517Cl and 3717Cl)
3517Cl 3717Cl Atomic # # P #e #n Mass # 35 37

16. Calculate All the # subatomic particles in the following atom with hyphen notation
Hyphen notation Symbol Atomic# mass # #p #e #n
Uranium U
Uranium U
Carbon C
Carbon C
Copper Cu
Copper Cu

18. Atom has two parts. At the center, there is ______1____charge due to____2_____ which have ____3______ charge. Intense mass at center is due to ____4_______ and _____5____ which are neutral. _____6__ and ___7______ have the same __8______. Negatively charged particles are called ___9_______ and these are located at out side ___10______. Atom has no charge because of # ___11___ ___12____ = #__ 13 _____Subatomic particles nucleus are collectively called _____14_____. # neutrons = ____15_____ - ____16_______. An atom has #p = 54, # n = 77, The name of the element is ___17_____ and it has ___18_______ electrons. It is neutral atom because of ___19_____ number of _____20___ and ____21_______.

19. Average atomic mass
There are 2 Type of marbles A and B. 30 marbles of A type have mass of 37gram each, and 70 marbles of B type marble have mass of 35 grams each. What is their average atomic mass
What are their relative abundances?
Relative abundance of A = Relative abundance of B =
# of A marbles x mass A
+ #of B marble x mass B
Average atomic mass = _________________________________
Total number of marbles
Does the average mass be closer to mass of A or mass of B marbles?
Average mass =

20. Carbon -12 is a standard atom
What is 1 atomic mass unit(amu)?
1C = ? Amu 1amu =
Average atomic mass = The average atomic mass of an element is the weighted average mass of isotopes of that element.
Two isotopes of chlorine 3517Cl and 3717Cl have
% abundance of 70% and 30% respectively. What is its average atomic mass? It is closer to isotopes ---- Why?

21. 1) 99. 9885 % atoms of hydrogen -1 has mass 1amu, and
1) % atoms of hydrogen -1 has mass 1amu, and .0115% atoms of hydrogen -2 has mass 2amu. What is its average atomic mass? 2) 98.93% carbon -12 has mass = 12 amu, and 1.07 % carbon has mass = 13 amu. Calculate average atomic mass

22. 3) There are three isotopes of oxygen. 99
3) There are three isotopes of oxygen % Oxygen-16 has mass of amu, 1.07% oxygen-17 has mass of amu, and 0.205% oxygen has mass of amu. Calculate average atomic mass of oxygen.
4) 69.15% copper-63 has mass = amu, whereas % copper -65 gas mass = amu. What is its Average atomic mass? Is the average atomic mass be closer to Cu-63, or Cu-65?