Foundation Chemistry Flashcards
What is an ion
An atom which has gained or lost valence electrons to gain a full valence shell to become stable.
How are atoms held together in ionic bonding?
By strong electrostatic forces.
Groups/Periods
Groups: same number of valence electrons
Periods: Same number of electron shells
Why are atoms electrically neutral
Because the number of positive charges (due to protons) is the same as the number of negative charges (due to electrons) and neutrons do not carry charge.
How are the electron shells located
Increasing distance from the nucleus.
How many electrons can be held in the 4th electron shell?
up to 18 (for elements with atomic number above 20)
Why are the group 18 elements called INERT gases?
Because they all have the maximum number of electrons in the outer energy level so they are stable as they are chemically unreactive.
What is octet rule
That the atoms of the first 20 elements are most stable when their valence shell contains 8 electrons.
Except for hydrogen, helium, lithium and beryllium which all become stable with 2 (or 0 for H) valence electrons.
How to name ions
Cations: named after element. eg Ca2+ = calcium ion
Anions (neg monoatomic ions): usually end in “ide” eg Cl= = chloride, O2- = oxide
Polyatomic ions: usually end in “ate” eg SO4(2-) = sulphate. Except OH- (hydroxide) and ammonium ion (NH4)
What is an ionic compound
when an anion bonds with a cation.
How are ions arranged in an ionic compound?
In a 3D lattice. This means that each cation is surrounded by anions, and in turn, each anion is surrounded by cations.
Lattice = regular, grid-like distribution pattern.
What is the ionic bond
The force of attraction that holds ions together in an ionic substance. These bonds arise because of the strong electrostatic attractions between the oppositely charged ions.
A cation (usually a metal) has a positive charge because it has lost electrons, meaning it has more protons than electrons. An anion (usually a non-metal) has gained one or more electrons, so there are more electrons than protons, meaning more neg charge than pos charge, so the anion is negatively charged.
Reactivity of metals in periodic table
Reactivity increases down the group as their ability to form positive ions increases. This is because the forces of attraction between the positive nucleus and the outer negative electrons are weaker due to the increased space between them, so it is easier for the larger atoms down the group to lose the valence electron. Less E required to lose electron.
Reactivity of non-metals in period table
Reactivity (ability to form anions or covalent bonds) decreases down a group.
