Chapter 3 Atoms and Elements The Atom Atomic Number and Mass Number Ions & Isotopes

Atomic Theory Atoms are building blocks of elements Similar atoms in each element Different from atoms of other elements Two or more different atoms bond together to form compounds

History of the atom Not the history of atom, but the idea of the atom Original idea Ancient Greece (400 B.C..) Democritus Greek philosopher

Hyle Another Greek Aristotle - Famous philosopher All substances are made of 4 elements Fire - Hot Air - light Earth - cool, heavy Water - wet Blend these in different proportions to get all substances Hyle

. e- nucleus

Who’s Next? Late 1700’s - John Dalton- England Teacher- summarized results of his experiments and those of other’s In Dalton’s Atomic Theory Combined ideas of elements with that of atoms

Dalton’s Atomic Theory All matter is made of tiny indivisible particles called atoms. Atoms of the same element are identical, those of different atoms are different. Atoms of different elements combine in whole number ratios to form compounds Chemical reactions involve the rearrangement of atoms. No new atoms are created or destroyed.

Location of Subatomic Particles 10-13 cm electrons protons neutrons 10-8 cm nucleus

Subatomic particles Actual mass (g) Relative mass Name Symbol Charge Electron e- -1 9.11 x 10-28 1/1840 Proton p+ +1 1.67 x 10-24 1 Neutron n0 1.67 x 10-24 1

Subatomic particles Relative mass Name Symbol Charge Electron e- -1 Mass (amu) Name Symbol Charge Electron e- -1 1/1840 Proton p+ +1 1 1 1 Neutron n0 1

Subatomic Particles Particle Symbol Charge Relative Mass Electron e- 1- 0 Proton p+ + 1 Neutron n 0 1

Counts the number of protons in an atom Atomic Number Counts the number of protons in an atom

Atomic Number on the Periodic Table 11 Na Atomic Number Symbol

All atoms of an element have the same number of protons 11 Na 11 protons Sodium

Learning Check State the number of protons for atoms of each of the following: A. Nitrogen B. Sulfur C. Barium

Solution State the number of protons for atoms of each of the following: A. Nitrogen 7 protons B. Sulfur 16 protons C. Barium 56 protons

Number of Electrons An atom is neutral The net charge is zero Number of protons = Number of electrons Atomic number = Number of electrons

All atoms of an element have the same number of protons and electrons 11 Na 11 protons 11 electrons Sodium

Atomic Mass Atomic mass is the weighted average mass of all the atomic masses of the isotopes of that atom.

Atomic Mass on the Periodic Table 11 Na 22.989770 Atomic Number Symbol Atomic Mass

Atomic Mass on the Periodic Table 11 Na 22.989770 Atomic Number Symbol Mass # 23 Atomic Mass

Mass Number Determined by : the whole Number closest to the atomic mass Counts the number of protons and neutrons in an atom

Atomic Symbols atomic number Show the mass number and atomic number Give the symbol of the element mass number Na sodium-23 atomic number 23 11

Subatomic Particles in Some Atoms O P Zn 16 65 31 15 30 8 8 p+ 15 p+ 30 p+ 8 n 16 n 35 n 8 e- 15 e- 30 e-

Isotopes Atoms with the same number of protons, but different numbers of neutrons. Atoms of the same element (same atomic number) with different mass numbers Isotopes of chlorine 35Cl 37Cl 17 17 chlorine - 35 chlorine - 37

Naturally occurring hydrogen consists of three isotopes, protium (H-1),deuterium (H-2), and tritium (H-3). State the number of protons, neutrons, and electrons in each of these atoms. 1H 2H 3H #p _______ _______ _______ #n _______ _______ _______ #e _______ _______ _______ 1 1 1

Naturally occurring hydrogen consists of three isotopes, protium deuterium tritium 1H 2H 3H #p 1 1 1 #e 1 1 1 #n 0 1 2 1 1 1

An atom of zinc - ( Zn-65) A. Number of protons in the zinc atom B. Number of neutrons in the zinc atom C. What is the mass number of a zinc isotope with 37 neutrons?

An atom of zinc - ( Zn-65) A. Number of protons in the zinc atom 1) 30 1) 30 B. Number of neutrons in the zinc atom 2) 35 C. What is the mass number of a zinc isotope with 37 neutrons? 3) 67

Write the atomic symbols for atoms with the following: A. 8 p+, 8 n, 8 e- ___________ B. 17p+, 20n, 17e- ___________ C. 47p+, 60 n, 47 e- ___________

Solution B. 17p+, 20n, 17e- 37Cl 17 47 16O A. 8 p+, 8 n, 8 e- 8 C. 47p+, 60 n, 47 e- 107Ag 47

IONS Na Cl Atoms with a charge (positive or negative) Atoms which gain or lose an electron atom ion #p 11 11 #e 11 10 #p 17 17 #e 17 18 1+ Na 1- Cl

IONS atom ion #p 12 12 #e 12 10 #p 8 8 #e 8 10 2+ Mg 2- O

Complete Atomic Symbol combines isotopes and ions Al Mass # 27 3+ Ionic charge Atomic # 13 13p+ 10e- 14n

Learning Check N P Zn 14 3- 65 2+ 32 3- 15 30 7 7p+ 15 p+ 30 p+ 7n 17 n 35 n 10e- 18 e- 28 e-

Example of an Average Atomic Mass Cl-35 is about 75.5 % and Cl-37 about 24.5% of natural chlorine. 35 x 75.5 = 26.4 100 35.5 37 x 24.5 = 9.07