Chapter 3: Atomic structure ....

Question 1

What is an atom?

Answer 1

• An atom is the smallest unit that makes up an element.
  -E.g. Oxygen is an element that is made up of only oxygen atoms while an atom is made out of neutrons, protons and electrons.

(Tip: An atom is NOT the same as an element because an atom is the smallest unit of matter that retains the chemical propeties of an element, while an element is a substance that is made up of only one type of atom.)

Question 2

What does an atom consist of?

Answer 2

• An atom consists of a nucleus, electron shells and sub-atomic particles, which include protons, nuetrons and electrons

Question 3

What are nucleons?

Answer 3

• Nucleons are protons and neutrons.

Question 4

Where are the sub-atomic particles found in an atom?

Answer 4

• The protons and neutrons are found in the nucleus, while the electrons are found in the electrons.
  -E.g. A berylium atom has 4 protons and 3 neutrons in its nucleus and 4 electorns arranged in its 2 electron shells.

Question 5

What is the relative mass and charge of a proton in an atom?

Answer 5

Sub-atomic particle: Proton
Relative mass: 1
Relative charge: +1
Location in the atom: Nucleus

Question 6

What is the relative mass and charge of a neutron in an atom?

Answer 6

Sub-atomic particle: Neutron
Relative mass: 1
Relative charge: 0
Location in the atom: Nucleus

Question 7

What is the relative mass and charge of an electron in an atom?

Answer 7

Sub-atomic particle: Electron
Relative mass: 1/1840
Relative charge: -1
Location in the atom: Electron shell

Question 8

What is the mass of an electron?

Answer 8

• The mass of an electron can be considered negligible.
• The number of protons in an atom is equal to the number of electrons.

Question 9

Why is an atom electrically neutral?

Answer 9

• An atom is electrically neutral as the number of positively chagred protons is balanced by an equal number of negatively charged electrons.

Question 10

What is a proton number?

Answer 10

• A proton number is the number of protons in an atom.

Question 11

What is the nucleon/mass number?

Answer 11

• The nucleon/mass number is the number of protons and neutrons (nucleons) in an atom.

Question 12

What is a nuclide notation?

Answer 12

• A nuclide notation can be used to represent the proton number and nucelon number of an element.
• E.g.
  35
  (Cl)
  17
  represents a chlorine atom with 17 protons and 35 nucleons, thus a chlorine atom has 35-17 = 18 neutrons.

Question 13

What is an ion?

Answer 13

• An ion is formed when an atom/a group of atoms loses or gains electrons.
• E.g. of ions: NA+, Mg2+, F-, and DH-

Question 14

What is the charge of an ion?

Answer 14

• The charge of anion shows the number of electrons that are lost/gained.
• E.g. #1: The Na+ ion has a charge of +1, so there is one more proton than electron in the Na+ ion. So the Na atom loses one electron to form the Na+ ion.
• E.g. #2 : The F- ion has a charge of -1, so this shows that there is 1 more electron than porton in the F- ion. So the F atom gais one electron to form the F- ion.

Question 15

What are isotopes?

Answer 15

• Isotopes are atoms of the same element with the same proton number but different nucleon number.
• E.g. Carbon 12 and carbon 14 are isotopes and both of them have 6 protons, but carbon 12 has 6 neutrons, while carbon 14 has 8 neutrons.

Question 16

Does isotopes have the same numebr as electrons (in an atom) ?

Answer 16

• YES, isotopes have the same number as electrons so they have similar chemical properties, BUT they have different physical properties such as density, melting point and boiling point.

Question 17

What is an atom made out of?

Answer 17

• An atom has one or more electron shells
• The first/inner most shells with the lowest energy level, and it is the closest to the nucleus.
• The outermost shell is the highest energy level and it is the furthest from the nucleus.

Question 18

What is electronic configuration?

Answer 18

• Electronic configuration refers to the arrangement of electrons in an atom and the electrons occupy the inner shells with the lowest energy first.

Question 19

What does the first/inermost, secod and third electron shell consist of?

Answer 19

• The first/innermost electron shell contains at most 2 electrons.
• The second and third electron shells can contain at MOST 8 electrons (maximum).

Question 20

What is the valence shell?

Answer 20

• The valence shell is the outermost electron shell.

Question 21

What is the valence electrons?-

Answer 21

• Valence electrons are the electrons found in the outermost shell.

Question 22

What is the electronic configuration and structure of hydrogen?

Answer 22

• Hydrogen has 1 electron, so its electronic configuration is 1.

Question 23

What is the electronic configuration and structure of lithium?

Answer 23

• Lithium has 3 electrons, so its 1st electron shell is filled with 2 electrons, while its 2nd valence shell is filled with 1 electron.
• Thus its electronic configuration is 2 and 1.

Question 24

What is the electronic configuration and structure of sodium?

Answer 24

• Sodium has 11 electrons, so its 1st electron shell is filled with 2 electrons while its 2nd shell is filled with 8 electrons, and its 3rd valence shell is filled with 1 electron.
• Thus its electronic configuration is 2,8,1/

Question 25

What is helium and argon?

Answer 25

• Helium and argon are both noble gases and group 18 elements.
• Helium and argon have 2 valence electrons and 8 valence electrons respectively, so their valence shells are full and they are STABLE and UNREACTIVE.

Question 26

Are atoms that have valence shells that are NOT FULL, reactive?

Answer 26

• YES, atoms with valence shells that are not full are reactive.
• They tend to gain/lose/share electrons to achieve the stable electronic configuration of a noble gas.