atomic structure and bonding Flashcards
atom
smallest particle of an element
atom structure
nucleus, proton, and neutron
-mass is concentrated in the tiny nucleus
Atoms are electrically neutral (can gain or lose electrons).)
negative ion=gains 1 or more electrons
positive ions=lose 1 or more electrons
atomic number/atomic mass
mass number= #of protons and neutrons
atomic number+# of protons and number of neutrons
*mass is always bigger
isotopes
same number of protons but different numbers of neutrons
*chemically similar but are slightly different in mass and density
relative atomic mass
weighted average of the relative isotopic masses, taking into account their relative abundance in nature
8 mass of an individual isotope of each element compared to the standard
Quantum mechanical model
The quantum model purpose is to show that electrons are found in regions of space around the nucleus that correspond to energies. These regions are called the energy levels of shells.
The number of electrons an energy level can hold is 2n^2.
electron configuration
The electron configuration of an atom shows the electrons and the energy levels they occupy.
E.g. Cl=2.8.7
O=2.6
*NOTE: K AND CA DEVALUTE FROM WHAT WE EXPECT
trends across a period
- atomic radium decreases; same energy level= same size
- Ionisation energy increases—valence electrons help more strongly by force of attraction
- Electronegativity increases—greater force of attraction
- Metallic character decreases: greater force of attraction and high electronegativity
-> attract electrons
trends down a group
- atomic radius increases; more added further away from nucleus
- Ionisation energy decreases further away-nucleus+ shielding effect
- Electronegativity decreases- little force of attraction
- Metallic character increases-metals give up electrons easily
atomic radius
size of the atom from the centre of the nucleus to the outermost electron.
ionisation energy
energy required to remove an electron from an atom (in gaseous state)
*the smaller the atom the harder it I to remove it, the bigger the easier.
electronegativity
electron attracting power.
yellow: want to lose electrons, red: want to add more electrons
yellow- down
red accross
periods and groups
For the element, the group (downwards) number indicates the number of valence electrons
*For an element: the period (horizontal) number tells us how many energy levels have electrons, and which level the valence electrons are in. (shells)
successive ionisation energy
the energy that is required to remove the electron one after the other
remove electrons and measure the ionisation energies
*the greater the attraction between the outer electrons and the nucleus, the greater the ionisation energy
3 factors affecting ionisation energy
- atomic radius: as it ↑, the force of attraction ↓
- charge on the nucleus: # protons= the ↑ force of attraction
- Shielding: electrons in the outer shell are repelled by electrons in the inner shell
shielding effect ↓ the attraction between outer shell and nucleus.
bonding
- atoms will bond together to get the electron configuration of a noble gas, (a full outer shell) because they are chemically stable
This involves getting 8 electrons in their outer energy level (except H or He, which only need 2)(Octect rule)
They can only do this by transferring or sharing electrons
types of bonding
- metallic
- ionic
- covalent- molecule
network
-network
metallic
metal atoms have low electronegativity when other metals are close by
valence electrons are attracted towards them
electrons are delocalized
electron sea model
metal ions- positively charged nucleus
*delocalised electrons
properties of metals
(a) high melting and boiling points
There is a strong electrostatic force of attraction between the positive and negative charge
(b) good conductors of heat and electricity
- the delocalised electrons are able to carry the electric charge or heat energy (kinetic) throughout the lattice structure.)
(c) Lusture(shiny)
- the delocalised electrons can reflect light as they move around
(d) malleable—made into sheets and ductile—drawn into wires
The metallic bond is nondirectional (due to the delocalized electrons)
when a disruptive force is applied to the metal , the electrons rearrange themselves, reforming the bond
metal ions line up with delocalised ectrons around it
ionic compounds
Made up of a positive cation(form a metal atom that has lost electrons)
and a non metal anion that has gained electron(s)
The metal cation always goes first
in a formula on name followed
by the ion metal anion.
- exception is NH4+
writing formula for ionic compounds
(a) simple binary- monatomic ions joined together
Use valence for these and make sure the charge is neutral
Ca O
-can also use lewis dot diagrams
-only valence electrons electrons (transfer)
Try to get a full outershell
metal usually doesnt have the dots around it
-the oppositely charged ions are strongly attached to one another and form a 3D lattice
properties of Ionic solids
(1) high melting and boiling point- there is a strong force of attraction between the positive and negative ions
(2) brittle- when a strong force is applied to the solid, like charges become aligned and the force of repulsion is greater then the force of attraction , the solid shatters
(3) conduct electricity in solution (aq) and molten (L) form, but not solid (s) form. in a solid , there is no free ions, but in aqueous and molten form
The ions are dissociated and are free to move and conduct electricity
covalent bonding
- a covalent bonding occurs when non- metal atoms bond to other non-metal atoms.
because non- metal atoms have similar electronegativity, they will share electrons to get a full outer shell
- covenant bonds are directional this means the electrons are attached to a particular atoms
- covalent substances are named by identifying the elements, using prefixes such as di, tri, tetra etc after the element and the second element has -ide after it
e.g. CO2=carbon dioxide
N2O4= dinitrogen tetraoxide
Use the Lewis dot diagram
intra-inter molecules
Intramolecular forces are those within the molecule that keep the molecule together, for example, the bonds between the atoms
ClIIIICl strong
Intermolecular forces are the attractions between molecules, which is weak
properties of covalent molecules
(1) mainly gases or liquids at room temperature- inter molecular forces holding molecules together are weak
(2) non conductors- the covalent bond is directional. There are no free ions or electrons to carry the charge
covalent networks properties
- a) do not dissolve in any solvent
- (b) have very high melting points
- (c)usually non conductors of heat and electricity
- (d)chemically inert
- (e)extremely hard and brittle
diamond
each carbon atom is attached to 4 other carbon atoms by single covalent bonds.this arrangement is repeated. throughout the whole molecule→gives diamond its properties of strength and rigidity
structure/lattice
graphite
graphite-has properties very unusual to a network solid (electrical, conductivity) because of its structure graphite can be used as a lubricant-the sheets of carbon atoms slide over one another
layers/sheets
Graphite and diamond are ALLOTROPES ( same substance but in a different form) of carbon
weakest to strongest
covalent molecular, metallic, ionic, covalent network being the strongest
what is most likely to be a covalent network?
metalloids:
B C Si Ge As Se Sb Te
