Chapter 2 Flashcards
What are ions?
Positively or negatively charged atoms
When are ion formed?
When electrons are transferred from one atom to another
What are cations?
Positively charged ions
What are anions?
Negatively charged ions
Generally, what is the charge on a metal ion equal to?
Its group number
Generally, what is the charge on a non-metal ion equal to?
Its group - 8
What does electrostatic attraction do?
It holds positive and negative ions together
What is an ionic bond?
The strong electrostatic attraction between 2 appositely charged ions
When does an ionic compound form?
When oppositely charged ions for an ionic bond
What 2 things affect the strength of an ionic bond?
The ionic charges and the ionic radii
How do ionic charges affect the strength of the ionic bond?
The greater the charge on an ion, the stronger the ionic bond
What is the relationship between the charge dennsity of an ion and the strength of an ionic bond?
The higher the charge density, the stronger the ionic bond
What is the relationship between the ionic radii and the strength of an ionic bond?
Smaller ions pack together closer together than large ions, so small packed ions have stronger ionic bonding than larger ions, which sit further apart
What happens to the ionic radius as you go down a group?
It decreases
What are isoelectronic ions?
Ions with different atoms with the same number of electrons
What happens to the ionic radius of isoelectronic ions as the atomic number increases?
The ionic radius decreases
What do dot-and-cross diagrams show?
The arrangement of electrons in an atom or a bond, and which atom the electrons in a bond originally came from
What structures do ionic compounds form?
Giant ionic lattice structures
What structure are ionic crystals?
Giant lattices of ions
What is a lattice?
A regular structure
What is a giant lattice?
A structure made up of the same basic unit repeated over and over again
Why does a giant lattice form?
Because each ion is electrostatically attracted in all directions to ions of the opposite charge
As ionic compounds have high melting points, what does this tell you?
The ions are held together by strong attraction
Why is an ionic compound soluble in water, but not in non-polar solvents?
The ions are pulled apart by polar molecules as they are charged
Why can ionic compounds conduct when molten, but not when solid?
Because their ions are fixed when solid, but free to move when molten
Why can’t ionic compounds be shaped?
Because the repulsion between ions would be very strong, so ionic compounds are brittle
When you electrolyse a green solution of copper chromate on a piece of wet filter paper, what colour does the filter paper turn at the cathode and anode?
Blue at the cathode and yellow at the anode
What does isoelectronic mean?
Having the same number of electrons
When are molecules formed?
When 2 or more atoms bond together, that are held by covalent bonds
What is a covalent bond?
A covalent bond is when atoms share electrons
How many electrons make up a covalent bond?
2 electrons
Why is 8 electrons (a full outer shell) good for the atom?
It is very stable
In covalent bonds, what is the positive nuclei attracted to?
The area where the shared electrons are
What is the bond length?
The distance between the 2 nuclei is the distance where the attractive and repulsive forces balance each other (bond length)
What is the relationship between the electron density and the bond length?
The higher the electron density between the atoms, the stronger the attraction between the atoms and the shorter the bond length
What is the relationship between bond enthalpy and bond length?
The shorter the bond length, the higher the bond enthalpy is
What is dative covalent bonding?
Where both electrons come from 1 atom. One atom donates 2 electrons to a bond
How is the ammonium ion NH4 + formed?
When the nitrogen atoms in an ammonia molecule donates a pair of electrons to a proton H+.
How is dative covalent bonding shown in a diagram?
By an arrow pointing away from the donor atom
What does the molecular shape depend on?
The number of pairs of electrons in the outer shell of an atom
Why do electron pairs repel each other?
Because electrons are all negatively charged, so electron pairs will repel.
What repel more, lone pairs of electrons or bonding pairs of electrons?
Lone pairs of electrons
Why are lone pair/lone pair angles the biggest in molecules?
Because they repel each other the most
Why are the bonding pair/bonding pair angles the smallest in molecules?
They repel each other the least
In methane (CH4) where there are no lone pairs of electrons, what are all the bond angles?
109.5 degrees
In ammonia, where there is 1 lone pair of electrons, what are all the bond angles?
107 degrees
In water, where there are 2 lone pairs of electrons, what is the bond angle?
104.5
When there are 2 electron pairs around a central atom, what are the bond angles?
180 degrees
What are linear molecules?
When the bond angle around an atom is 180 degrees