The Atom Flashcards
Atom Intro, Periodic Table and Chemical Bonding
Describe the structure of the atom
What is an atomic number?
An atomic number represents and is equal to the number of protons an element has
What is mass number?
The sum of the mass of the total number of protons and neutrons
What are isotopes?
They are the same element with a different number of neutrons that have different abundance in nature and have different properties compared to each other
Outline Neil Bohr’s Visualisation of The Atom
The atomic number (z) is equal to the total number of electrons
protons and neutrons exist in equal proportion within the nucleus of the atom
electrons exist in a cloud around the nucleus and occupy shells
the valence shell is the outermost electron shell of an atom
Describe “atomic radius” and its trends within the periodic table
Atomic radius decreases across a period, due to increasing electrostatic interaction - less distance from the nucleus
Atomic radius increases down a group, due to increased shielding from inner shells - more distance from the nucleus
Describe “ionic radius” and its differences from “atomic radius”
when electrons leave, or are added, to the valence shell of an atom they change the ratio of protons to electrons, and therefore the overall charge of the atom changes
when cations + are formed the IR is less than the AR due to a greater relative positive charge
when anions - are formed the IR is larger than the AR due to a smaller relative charge
Describe “ionisation energy” and its trends within the periodic table
Ionisation energy is the amount of energy required to remove an electron from an atom
IE is inversely proportional to AR, due to increased electrostatic attraction between protons and electrons
increases across a period and decreases down a group
What is “electronegativity”?
the ability of an atom to attract shared electrons to itself
increases along a period and decreases down a group
What is “electron affinity”?
how likely an atom is to receive an electron
ionic bonds
increases along a period and decreases down a group
What is the main drive for atoms to bond with one another?
to completely fill their valence shell as it enables greater stability
“the rule of two” - period 1 elements
“octet rule” - period 2 - 7 elements
What is the typical number of electrons in the valence shell of Metals?
0-3, so “easier” to give away electrons
typical form cations
What is the typical number of electrons in the valence shell of Non-Metals?
5-7, so “easier” to take electrons to satisfy the “octet rule”
typically anions
Describe “Ionic Bonds”
forms between a metal and a non-metal, when ¡ or more electrons are exchanged between the two
when an atom loses an electron it becomes ionized, metals form cations
when an atom gains an electron and becomes ionized, non-metals form anions
Describe “Covalent Bonds”
two non-metal bonds through the sharing of electrons (1-4) from their respective valence shells to satisfy their octet
