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Unit 1 Principles and Applications of Science I
Terms in this set (35)
Occurs when an atom loses one or more electrons and donates it to an an atom of a different element.
The atom which loses electrons becomes positively charged and the atom which gains electrons becomes negatively charged due to the imbalance of protons and electrons.
when the opposite charges on the ions are what hold them together.
Occurs between atoms of two non-metals . It is formed when an electron is shared between the atoms
Are giant structures of atoms which are held together by metallic bonds. The structure is a regular lattice.
it is caused because the electrons in the highest energy level of a metal atom has the ability to become delocalised which means that they are free to move through the metal in a sea of electrons which gives the metal nuclei a positive charge. This positive charge is attracted to the negative charge on the delocalised electrons which causes a strong force of attraction between the positively charged nuclei and the negatively charge delocalised electrons
Why metallic bonding is caused
is determined by what type of bond will form between them.
there is a strong electrostatic attraction between the two nuclei and the shared pairs of electrons between them. This is the covalent bond. Both of the atoms have the same electronegativity and so the electrons are equally shared
The molecule is non-polar.
Most covalent compounds, the bonding is polar covalent. The shared electrons are attracted more to one nucleus in the molecule than the other. The atom with the higher electronegativity will attract the electrons more strongly. This gives the atom a slight negative charge and the other atom in the molecule will have a slight charge.
When the electron distribution in a molecule becomes non-symmetrical, then one end of the molecule can become more positive and one end becomes more negative which causes a temporary dipole. The positive and negative charge can disturb the electrons in a nearby molecule, repelling the electrons and causing a dipole in that molecule. The molecule with the temporary dipole and the molecule with the induced dipole attract each other and pull the molecules together.
The forces are temporary because the electrons are constantly moving, so the electron density in any part of a molecule is constantly changing.
London dispersion forces (temporary dipole)
Are permanent forced between polar molecules. Polar molecules have a permanent negative end and a permanent positive end. These oppositely charged ends attract each other.
Dipole-dipole forces are slightly stronger than London dispersion forces but are still weak in comparison to a covalent bond.
The strongest form of intermolecular forces. Are a special type of dipole-dipole bond and are forces that are about 10% of the strength of a covalent bond
Will form when compounds have hydrogen directly bounded to fluorine, oxygen or nitrogen. This is because there is a large difference in electronegativity between hydrogen and these three atoms. The difference means that very polar bonds are formed.
Is the actual mass compared to the theoretical mass. An efficient process would give a percentage yield as close to 100% as possible
Percentage = actual mass/theoretical mass x 100
Percentage Yield equation
the minimum energy needed for one mole of the outermost electrons to be removed from one mole of atoms in a gaseous state.
It decreases down a group.
First ionisation energy
the ratio of the amount in moles of each substance in a chemical reaction
the higher the tendency is to lose an electron and from a complete shell. The more reactive a metal is, more difficult it is to extract from its ore and more likely to be found in a compound.
a type of chemical reaction that involves a transfer of electrons between two species.
OilRIG - oxidation is lost, reduction is gained
1. elements = 0
2. ion = charge
3. fluorine = - 1 most electronegative
4. oxygen = -2 (except in preoxides and fol)
5. Chlorine = -1 (unless bounded with F & O)
6. hydrogen = +1 (when bounded to a metal)
general rules for redox reactions
Shows the simplest whole number ratio of atoms of each element in a compound.
Shows the number and type of atoms present of each element present in a compound
Atomic radius decreases across a period due to the increase in nuclear charge. The number of shell remain the same so the outer electrons are more strongly attracted to the nucleus.
Ionic radius decreases down the group.
Trends in the periodic table
Electronegativity increases up a group as the bonding electron pair in the covalent bond will be closer to the nucleus attracting it
It also increases across a period as the nuclear charge attracting the bonding electron pair is greater
Trends in the periodic table
Melting and boiling points increase as the metallic bond strength increases. The positive metal ions get smaller across the period, their charge gets larger and there are more delocalised electrons
Trends in the periodic table
the charge of the ions affects the melting point of an ionic compound because the greater the charge, the greater the electrostatic attraction, the stronger the ionic bond, the higher the melting point.
The size of the ions also affect the M&B points of ionic compounds because smaller ions pack close together than larger ions, the electrostatic attraction is greater which causes the compound to be stronger. The more electrons a positive ion has, the more shells therefore the radius is bigger.
Factors that affect the Melting and boiling points of an ionic compound.
electrons fill the orbital with the lowest energy. State first relation to how close it is to the nucleus. This allows the most stable electron configuration possible.
Electrons can be moved into different orbitals with the addition of energy. When the energy is removed, the electrons return to their ground state, emitting a corresponding amount of energy
When a more reactive element displaces a less reactive element in a solution.
When two atoms have the same electronegativity and electrons are shared equally
Shared electrons are attracted more to one nucleus in the molecule than the other unequal. The atom with higher electronegativity will attract the electrons more strongly.
1. High melting points
2. Good conductors of electricity
3. Good conductors of heat
4. High density
Physical properties of metals.
As metals are giant lattice structures, the number of electrostatic forces to be broken is extremely large and so metals have high melting and boiling points. This means that the melting point and boiling point of metals are similar to those for ionic compound than for covalent substances.
Why metals have high melting and boiling points
Metals can be bent and shaped without breaking. this is due to the fact that they consist of layers of atoms that can slide over one another when the metal is bent, hammered or pressed
Why metals are malleable
Metals are described as ductile. This is because of the ability of the atoms to roll over each other into new positions without breaking the metallic bond
Why metals are ductile
Metals are good conductors of electricity and heat because the atoms in the metals form a matrix through which outer electrons can move freely and the electrons then move freely throughout the electrons sea.
Why metals are good conductors of electricity and heat
The energy change that occurs when an atom gains an electron, releasing energy in this process. An electron is negatively charged so when an atom gains electrons, an energy change occurs.
Reducing agent: is the reactant that is being oxidised, removing oxygen
Oxidising agent: reactant that is being reduced providing the oxygen.
Reducing and oxidising agent.
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