Download The Bohr Model of the Atom

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The Rutherford Model of the Atom
1) Complete the following chart: Read page 38 under the heading “Types of Atomic Particles”
Particle
Location in Atom
Charge
Relative Mass
electron
orbits
1-
approx. 0.00054 mp+
proton
nucleus
1+
approx. 1u
neutron
nucleus
0
approx. 1.0005 mp+
The Bohr Model of the Atom
Read Page 39 under the heading “The Bohr Model of the Atom”
2) a) Where are electrons held in the Bohr model of the atom?
Orbits
b) Can electrons be any distance they want from the centre of the atom?
c) Where are atoms the most stable?
No
The Noble Gas column.
3) Using some complex math, Bohr was able to work out how many electrons each shell could hold:
first shell
___2___
second shell
___8___
third shell
___8___
forth shell
___?___
The number of electrons equals the number of protons in a neutral atom.
Electron shells are filled from the first shell outwards.
Each element has a different arrangement of electrons, which can be represented by a Bohr Diagram.
To make a Bohr diagram: i) draw the symbol of the element with the number of protons and neutrons in it.
ii) figure out how many electrons the atom has
iii) draw a circle for the first electron shell
iv) add dots to the circle to represent electrons,
add no more dots that the shell can hold
and add no more dots than the atom actually has electrons
v) subtract the electrons used from the total
vi) if you still have electrons left, add another shell and repeat steps iv to vi
Examples:
4) On a separate sheet, draw Bohr diagrams for the elements C, Mg, Cl-, and K+.
1st shell
C
Mg
ClK+
2
2
2
2
2nd shell
4
8
8
8
3rd shell
2
8
8
4th shell
5) In a neutral atom, the number of protons must _equal___ the number of electrons.
Read page 38 under the heading “Important Atomic Numbers”
How we describe atoms:
Elements: depend on the Atomic number; the atoms of each element have a specific number of protons.
Isotopes: - Not all atoms of an element are exactly alike.
- They all have the same number of protons, but may have different numbers of neutrons
- Atoms of the same element, but different numbers of neutrons are called isotopes.
- Different isotopes have the same chemical properties, but different masses.
- Thus, a heavier atom which behave the same as a lighter atom of the same element, but
substances made out of the heavier atom will be heavier and have slower evaporation rates.
Ions:
if an atom gains or loses electrons, it is no longer neutral, it is charged.
if it gains electrons, it will have a negative charge (more electrons than protons)
if it loses electrons, it will have a positive charge (more protons than electrons)
6) a) What is the charge of an atom that has 13 protons and 10 electrons?
b) What element is it?
C = #p+ - #e- = 13 - 10 = 3
Aluminum (Z=13)
7) a) What is the mass number of an element with 3 protons and 4 neutrons? A = #p+ + #no = 7
b) What element is it?
Lithium (Z=3)
8) a) How many neutrons does an atom have if it has 6 protons and a mass number of 13? N = A-Z=13-6=7
b) What element is it?
Carbon
9) How many protons does an atom have if it has a mass number of 14 and 8 neutrons? Z=A-N=14-8=6
Carbon
10) Which of the following atoms are different isotopes of the same element?
b) 11 p+, 12 no, 11 ec) 12 p+, 12 no, 12 ea) 12 p+, 13 no, 10 ea and c (same #p+ (Z), different number of neutrons);
11) Which of the atoms in question 10 are ions? a, b (#p+ - #e- <>0)
12) Which of the atoms in question 10 has the largest mass number? a, A = 25
13) Which of the atoms in question 10 is not the same element as the other two?
b, Sodium rather than Magnesium
14) How many protons, neutrons, and electrons do the following atoms have?
8, 8, 10; 16, 17, 16; 5, 6, 5
15) What are the atomic numbers and mass numbers and charges of each of the atoms in question 14?
8, 16, -2; 16, 33, 0; 5, 11, 0