Chapter 3: Atomic Structure Flashcards
What are atoms made up of?
Atoms are made out of 3 sub-atomic particles. These particles are proton, electron, and neutron.
What are some characteristics of these sub-atomic particles?
Proton: - Represented by the letter, p
- Found in the nucleus
- Relative mass=1
- Relative charge= +1
Neutron: - Represented by the letter, n
- Found in the nucleus
- Relative mass=1
- Relative charge=0
Electron: - Represented by the letter, e
- Found in electron shells around the nucleus
- Relative mass=0
- Relative charge= -1
What is the electrically neutrality of atoms?
-An atom contains an equal number of positively charge protons and negatively charged electrons.
-Thus, the positive and negative electric charges cancel out exactly.
What is a proton number and what are its properties?
-The number of protons in an atom is called its proton number.
-It is also known as the atomic number.
-Since an atom is electrically neutral (no overall charge), proton number=number of electrons
-Each element has an unique proton number.
-Atoms of different elements have different proton numbers.
-The proton number is usually found at the top/the smaller number is always the proton number in the periodic table.
What is a nucleon number and its properties?
-The total number of protons and neutrons in an atom is called the nucleon number. (electron=proton. hence it is negligible in the nucleon number)
-Nucleon number is also known as the mass number/relative atomic mass.
-The mass of an atom depends on the number of protons and neutrons.
-Nucleon number= number of protons + number of neutrons
-The nucleon number can be found at the bottom/is always the bigger number in the periodic table.
How can we find the number of neutrons given the nucleon number and the proton number of an element?
Number of neutrons = nucleon number - number of protons
What are ions?
-When an atom loses or gains electrons, an ion is formed. (no. of protons is not equal to the no. of electrons)
An ion is an atom that:
-carries a positive or negative charge as a result of having an unequal number of protons and electrons.
What are negative ions and how is it achieved?
An atom that has gained electrons will have more electrons than protons. Hence, the atom will have a negative charge.
-A negative ion (anion) is formed.
What are positive ions and how is it achieved?
An atom that has lost electrons will have more protons than electrons. Hence, the atom will have a positive charge.
-A positive ion (cation) is formed.
What are isotopes and its properties?
Isotopes are atoms of the same element with the same number of protons but different number of neutrons.
Properties of isotopes:
- Isotopes have the same chemical properties and take part in the same type of chemical reactions (react in a similar manner)
- Chemical properties of a substance are determined by the type of chemical reactions it undergoes.
- Isotopes have different properties (dependent on mass number)
- Isotopes have a different number of neutrons, resulting in different masses.
- The difference in mass causes difference in densities, melting and boiling points etc.
Summary:
- Isotopes have the same no. of protons and electrons
- They have similar chemical properties.
- They have different number of neutrons. Hence, they have different mass number.
- They have different physical properties e.g. melting point.
What is an electronic configuration and what are the steps to electron arrangement?
Electrons move around the nucleus in regions known as electron shells.
Electronic configuration/structure is the arrangement of electrons in an atom.
Electronic Configuration
The first shell:
- is closest to the nucleus;
- holds a maximum of 2 electrons
- is always filled first
- has the lowest energy level
The second shell:
- can hold up to 8 electrons
- is filled after the 1st shell;
- has higher energy than 1st shell.
The third shell:
- can usually hold up of 8 electrons;
- is filled after the 2nd shell.
- has higher energy than 2nd shell.
Steps to draw electronic structure:
1. Find the proton number.
2. Since atoms are electrically neutral, number of protons = number of electrons
3. Fill electron shell with electrons starting from the shell closest to the nucleus.
How are elements arranged in the Periodic Table?
Elements are arranged in order of increasing proton number.
There are 18 vertical columns called Groups.
There are 7 horizontal rows of elements called Periods.
- Elements with the same number of valence electrons belong to the same group in the Periodic Table.
Example:
Sodium (2, 8, 1) and Potassium (2, 8, 8, 1) both have 1 valence electrons and belong to Group 1
Hence, elements in the same group of the Periodic Table have similar properties.
-Elements with the same number of electron shells belong to the same period in the Periodic Table.
Example:
Fluorine (2, 7) and Boron (2, 3) both have 2 electron shells and belong to Period 2.
