Download Unit 4 – Atomic Structure Study Guide

Unit 4 – Atomic Structure Study Guide
1. List the components of Dalton’s Atomic Theory.
 All matter is composed of atoms
 Atoms of a given element differ from atoms of other elements
 Compounds are formed when atoms chemically combine in specific whole number ratios
 Chemical reactions change the way atoms are combined
2. Based upon Dalton’s Atomic Theory, explain the difference between a sodium atom and a chlorine
atom.
 Sodium and chlorine are different elements, so there atoms must be different
3. Based upon Dalton’s Atomic Theory, explain why Mg1.5Cl3 is not a valid formula.
 Dalton considered atoms to be whole and indivisible, that is, only whole atoms can be combined
to form compounds. In the above formula, there are 1.5 Mg atoms, which is not possible based
upon the indivisibility of an atom.
4. Complete the following table on the subatomic particles.
PARTICLE
Proton
LOCATION
Nucleus
CHARGE
+1
MASS (AMU)
1
Neutron
Nucleus
0
1
Electron
Electron cloud
-1
1/1836
5. Describe what Rutherford’s Gold Foil experiment showed about the structure of an atom.
 Rutherford shot alpha particles (“atomic bullets”) at a thin piece of gold foil – gold is very dense –
and measured where the alpha particles hit the detector. He found that most alpha particles
went straight through, with some being deflected to the side, and very few deflected back.
 He interpreted this to mean an atom was mostly empty space with a small dense core that has a
positive charge.
6. In the symbol,
, explain what 11, 23, and Na represent.
 11 – the Atomic Number (Z), which represents the number of protons and defines the element
 23 – the Atomic Mass (A), which is equal to the number of protons + the number of neutrons
 Na – the symbol for the element, which is sodium
7. Explain why 14C and 12C are isotopes.
 Isotopes are atoms that have the same Atomic Number (number of protons), but have a different
Atomic Mass, that is, isotopes have the same number of protons but a different number of
neutrons
 In the above, both contain the symbol C for the element (carbon), so the above are the same
element, which means they have the same Atomic Number (number of protons). The numbers 14
and 12 represent the Atomic Mass, so the atoms have different Atomic Mass. Thus, the atoms are
isotopes because they have the same Atomic Number but a different Atomic Mass.
8. Complete the following table.
SYMBOL
ATOMIC NO.
ATOMIC
MASS
NO.
PROTONS
NO.
ELECTRONS
NO.
NEUTRONS
8
16
8
8
8
13
27
13
13
14
2
4
2
2
2
6
13
6
6
7
20
40
20
20
20
9. Select the true statement.
a. There are more metals than nonmetals in the Periodic Table.
b. There are more nonmetals than metals in the Periodic Table.
10. True or False. The nonmetals are located on the left side of the Periodic Table.
11. Select the true statement.
a. All elements in the same Group/Family have similar chemical properties.
b. All elements in the same Period/Row have similar chemical properties.
12. Describe the trend in Atomic Radius in relationship to the Periodic Law.
 The Periodic Law states there is a repeating, rise-and-fall pattern.
 The Atomic Radius increases as you go across a row, then when you go the first element in the
next row down, the Atomic Radius gets smaller then increases as you go across this row.
 This pattern repeats when you go down then across each row in the Periodic Table.
13. Define the following:
a. ground state – all the electrons are located in their lowest possible energy level
b. excited state – through the absorption of energy, usually heat or light, an electron moves to a
higher energy level
14. Explain what happens during an electron’s transition from the ground state to an excited state and
the return to the ground state.
 An electron in the highest energy level of a ground state atom absorbs energy
 This increases the energy in the electron, which moves to a higher energy level creating an excited
state in the atom
 The atom remains in the excited state as long there is energy to absorb
 When there is no longer energy to absorb, the electron loses energy, which it emits usually as
heat or light, and the atom returns to the ground state
15. Describe the shape of and maximum number of electrons in the s and p orbitals.
 s oribital – has a spherical shape and holds a maximum of 2 electrons
 p orbital – has a dumbbell shape (there are 3 p orbitals, with one each along the x, y, and z axis)
and each individual p orbital will hold 2 electrons so the maximum number of p electrons for all 3
orbitals is 6.
16. In the electron configuration, He 1s2, explain what 1, s, and 2 represent.
 1 – represents the energy level of the orbital
 s – represents the orbital, in this case the s orbital, but also have a p orbital
 2 – the number of electrons in the orbital
 He – is the symbol for the element helium
17. Define the following terms and how their values can be obtained from the Periodic Table:
a. valence shell – the highest energy level containing electrons, which is obtained from the
element’s row in the Periodic Table
b. valence electrons – electrons located in the highest energy level, may be in more than one
orbital, for example, carbon has 4 valence electrons where 2 are in the s orbital and 2 are in the p
orbital. The A column number determines the number of valence electrons – carbon is in column
4A.
c. Lewis Dot Structure – uses dots distributed around the symbol of the element to denote the
number of valence electrons.
18. Give the electron configuration and Lewis Dot Structure for the following:
a. K 1s22s22p63s23p64s1
b. Ne 1s22s22p6
c. F 1s22s22p5