Chapter 03 - Atomic Structure Flashcards
What are atoms?
Atoms are the smallest particle of an element that can still have chemical characteristics of an element
What are the 3 sub atomic particles in an atom?
Protons and neutrons in the nucleus and electrons moving around the nucleus in the electron shell
What is the relative mass of a proton?
1
What is the relative mass of a electron?
1/1840
What is the relative mass of a neutron?
1
What is the relative charge of a proton?
+1
What is the relative charge of a electron?
-1
What is the relative charge of a neutron?
0
Why is an atom electrically neutral?
1) An atom has equal number of positively charged protons and negatively charged electrons.
2) The positive and negative charges cancel each other out.
3) Thus, an atom is electrically neutral and has no net charge.
Which 2 subatomic particles make up the mass of the atom?
Protons and neutrons
In an atom the proton number is also the ____ ____
Atomic number - shows number of protons
In an atom the mass number is also the ____ ____
Nucleon number - shows number of protons and neutrons
Number of protons = ?
(in an atom)
Number of electrons
Number of neutrons = ?
(in an atom)
Nucleon number - proton number
Element V
Nucleon number = 51
Proton number = 23
How many protons, electrons and neutrons are present in element V?
Proton = 23
Electron = 23
Neutrons = 28
What is a electronic configuration?
The arrangement of electrons in an atom
Where do the electrons have the most and least amount of energy?
Electrons in the inner electron shell has the lowest energy while electrons in the outer shell has the highest energy
What are the maximum electrons allowed in the first 3 electron shells?
First shell: 2
Second shell: 8
Third shell: 8
What is the valence shell?
The electron shell furthest from the nucleus
What are the electrons in a valence shell called?
Valence electrons
How can you use valence electrons to determine whether an element is a metal or non metal? (For the first 20 elements only)
The valence electrons of the first 3 elements (1,2,3) shows that the element is a metal
The valence electrons of the 4th to 20th element (4,5,6,7..) shows that the element is a non metal
When is an atom unreactive?
When the atom has a maximum number of electrons in the valence shell, it becomes stable and unreactive
What are the 2 characteristics of noble gases?
Inert and exists as monatomic elements
What are is the name of the group of elements in the periodic table that are stable?
Noble gases
Which atom has a duplet electronic configuration?
An atom with a maximum of 2 electrons in only the first electron shell, Helium
When does an atom have an octet electronic configuration?
An atom with a maximum of 8 electrons in the second or third electron shell, e.g Neon
How are elements in the periodic table arranged?
Elements are arranged in increasing proton number
What are isotopes?
Isotopes are atoms of the same element that have the same proton number but different neutron number, resulting in different nucleon number
Isotopes are expressed using their ____ ____
Nucleon number (e.g chlorine-35, chlorine-37)
What are the 2 similarities of isotopes?
1) Same number of protons and electrons
2) Similar chemical properties
What are the 2 differences in isotopes
1) Different mass number (due to neutron number)
2) different physical properties
What does the group number represent in a periodic table?
Number of valence electrons
What does the period number represent in a periodic table?
Number of valence shells
How are ions formed?
When an atom loses or gains electrons and the proton number is not equal to the electron number. This causes the atom to not be electrically neutral forming an ion
What is an ion?
An ion is a charged particle formed when an atom loses or gains electrons
What are the 2 types of ions?
Cations and anions
When do cations (+) and anions (-) form?
Cation: When an atom loses electrons
Anion: When an atom gains an electron
What do most atoms not have and seek for it?
Atoms do not have a stable electronic configuration (because their valence shell is not completely filled) and seek a noble gas configuration
In order to achieve a noble gas configuration, what do atoms do?
Atoms lose or gain electrons so that their valence shells will have the maximum amount of electrons
Usually do metals for cations?
Yes, metals often lose electrons to form cations while non metals gain electrons to form anions
What is the subatomic particle responsible for the chemical properties of an atom?
Electrons
What subatomic particles do not change when atom forms an ions?
Proton and neutron number
When a sodium atom becomes a sodium ion, how does it change in positive, negative and net charge and electronic configuration?
Sodium atom:
Positive charge: 11+
Negative charge: 11-
Net charge: 0
Electronic configuration: 2,8,1
Sodium ion:
Positive charge: 11+
Negative charge: 10-
Net charge: 1+
Electronic configuration: 2,8
When a fluorine atom becomes a fluoride ion, how does it change in positive, negative and net charge and electronic configuration?
Fluorine atom:
Positive charge: 9+
Negative charge: 9-
Net charge: 0
Electronic configuration: 2,7
Fluoride ion:
Positive charge: 9+
Negative charge: 10-
Net charge: 1-
Electronic configuration: 2,8
What is valency?
Valency refers to the number of valence electrons of an atom involved in gaining, losing or sharing
(E.g. atom gains/loses/shares 2 electrons, valency is 2)
What can valency help us find?
Chemical formula of a substance
e.g. Mg atoms lose 2 electrons to form Mg ions so the valency is 2
Cl atom gains 1 electron to form Cl ions so the valency is 1
When Mg and Cl combine, the chemical formula of magnesium chloride is found by exchanging their respective valency
MgCl2
What is relative abundance?
Relative abundance refers to the percentage of an isotope of an element compared to the total number of isotopes of the element
Element X has two isotopes:
Isotope X-90 → Mass = 90, Abundance = 25%
Isotope X-92 → Mass = 92
Abundance = 75%
What is the Relative Atomic Mass (Ar) of element X?
1) Convert percentages
25% = 0.25
75% = 0.75
2) Multiply
90 x 0.25 = 22.5
92 x 0.75 = 69.0
3) Add together
22.5 + 69.0 = 91.5
Since 25% and 75% = 100%, Ar = 91.5
Element Y has two isotopes:
Isotope Y-16 → Mass = 16
Isotope Y-18 → Mass = 18
The Relative Atomic Mass (Ar) of element Y is 17.2.
Find the relative abundances of the two isotopes.
1) Let 𝑥 be relative abundance
Let the relative abundance of Y-16 = 𝑥
Since the relative abundance of the isotopes add up 100%, the relative abundance of Y-18 will = 100 - 𝑥
2) Substitute into formula
17.2 = [ (16 x 𝑥) + (18 x (100-𝑥)) ] / 100
𝑥 = 40
3) Final values
Relative abundance for
Y-16 = 40%
Y-18 = 60%
Isotope Z-10 → Mass = 10, Abundance = 10%
Isotope Z-11 → Mass = 11, Abundance = 20%
Isotope Z-12 → Mass = 12, Abundance = 20%
Find the Ar of Z
1) Convert percentages into decimals
10% = 0.1
20% = 0.2
20% = 0.2
2) Multiply isotopes mass by abundance
10 x 0.1 = 1
11 x 0.2 = 2.2
12 x 0.2 = 2.4
3) Add them
1 + 2.2 + 2.4 = 5.6
Since 10% + 20% + 20% = 50% and not 100%, divide the total relative abundance as a decimal:
Ar = sum of mass x abundance / total abundance
50% = 0.5
5.6/0.50 = 11.2
Ar = 11.2
Element T has two isotopes:
Isotope T-25 → Mass = 25
Isotope T-27 → Mass = 27
The Relative Atomic Mass (Ar) of element T is 25.6.
1. Find the relative abundances of T-25 and T-27.
2. What is the percentage difference between the two abundances?
- 1) Let relative abundance of T-25 = 𝑥
Let relative abundance of T-27 = 100 - 𝑥
2) Substitute into formula
25.6 = [ (25 x 𝑥) + (27 x (100-𝑥) ] / 100
𝑥 = 70
3) Final values
Relative abundance for
T-25 = 70%
T-27 = 30% - 1) Find the difference in percentages
70% - 30% = 40%
2) Take the difference divided by the larger percentage abundance and times 100
(40/70) x 100
