All Modules - TERMS and FORMULAS to memorise

Question 1

Module 1 - The Atom

Brownian motion
It is the perpetual jiggling of particles that results from collisions between invisible atoms and visible particles.

Chemistry
The study of the subatomic behaviour.

Atom
Atom is made of even smaller particles, called subatomic particles (protons, neutrons and electrons). To date, we know of slightly more than 100 distinct atoms. Of these, about 90 are found in nature. Atoms are smaller than the wavelengths of visible light, this is why we cannot see them. But atoms can be “felt” using a device called a scanning probe microscope.

Atomic nucleus
The dense, positively charged center of every atom.

Answer 1

Proton
A positively charged subatomic particle of the atomic nucleus.

Neutron
An electrically neutral subatomic particle of the atomic nucleus.

Nucleon
Any subatomic particle found in the atomic nucleus: proton or neutron.
Electron
An extremely small, negatively charged subatomic particle found outside the atomic nucleus. An electron is about 2000 times smaller than a proton or a neutron.

Valence electron
An electron located in the outermost shell that can participate in chemical bonding.

Core electron
Any electron in an atom which is not in the valence shell.

Question 2

Module 1 - The Atom

Atomic number
A count of the number of protons in the atomic nucleus.

Atomic mass number
It is used to distinguish one isotope from another, it is the total number of nucleons that an atom contains.

Atomic mass
The average mass of all the isotopes of an element. It is the number given below the symbol in the Periodic Table, atomic mass numbers are not whole numbers. The atomic mass is measured in atomic mass units (amu), There is a relationship between amu and grams, both are units of mass, see the conversion formula below.

Answer 2

Element
Any material that is made up of only one type of atom.

Periodic Table
All of the elements are listed in a chart called the Periodic Table ,which has 18 groups (vertical columns) and 7 periods (horizontal rows).

Isotopes
Any member of a set of atoms of the same element whose nuclei contain the same number of protons but different numbers of neutrons. Isotopes of an element differ only by mass, not by electric charge. Our bodies can’t tell the difference between isotopes.

Percent abundance
Carbon-12 has a percent abundance of 99%, which means that 99 out of 100 carbon atoms are Carbon-12 isotopes.

Compound
Most materials are made from more than one kind of atom. These materials are called compounds.

Question 3

Module 14 - The Atom

Period
A horizontal row in the periodic table. The number of elements in each period is equal to the shell’s capacity for electrons. The first shell (first from the nucleus) can hold max 2 electrons. That’s why, we find only 2 elements, hydrogen and helium, in the 1st period. The second and third shells - each - can hold up to 8 electrons, so 8 elements are found in both the 2nd and 3rd periods, and so on.

Group
A vertical column in the periodic table, also known as a family of elements. Elements within the same group are organised according to the number of valence electrons.

Shell
A region of space around the atomic nucleus in which electrons may reside. In an atom, there are at least 7 shells, and each shell can hold only a limited number of electrons. By convention, each shell is assigned a number and the symbol n—for example, the electron shell closest to the nucleus is called 1n.

Answer 3

Octet rule
Most of the elements important in biology need a minimum of 8 electrons in their outermost shell in order to be stable. Helium (He), neon (Ne) and argon (Ar) are called inert or noble gases, because their outermost shells either are filled to capacity with electrons or satisfy the octet rule, which makes them highly stable as single atoms, so these elements are non-reactive.

Orbital
Electrons do not circle the nucleus, but rather spend most of their time in sometimes-complex-shaped regions of space around the nucleus, known as electron orbitals.

Subshell
It is a set of of one or more orbitals. Subshells are designated by the letters - s/d/p/f - and each letter indicates a different shape. For instance, s-subshells have a single, spherical orbital, while p-subshells contain 3 dumbbell-shaped orbitals at the right angle to each other. Most of organic chemistry involves interactions between electrons in s- and p subshells.