Chemistry - Exam Flashcards
What is the difference between atomic and mass number?
Atomic number is the number of protons in the nucleus or the number of electrons surrounding the nucleus while atomic mass gives the number of protons and neutrons located in the nucleus.
Atomic structure and configuration?
Atomic structure refers to the structure of an atom comprising a nucleus (centre) in which the protons (positively charged) and neutrons (neutral) are present. The negatively charged particles called electrons revolve around the centre of the nucleus. Configuration is:
1st shell = max of 2 electrons
2nd shell = max of 8 electrons
3rd shell = max of 18 electrons
What are valence electrons/ shells?
Valence electrons are the electron is a negatively charged particle, located in the outermost shell of an atom, that can be transferred to or shared with another atom. While valence shells are the outermost shell of an atom containing the valence electrons.
Valence electrons are the easiest to remove and determine how an element reacts. When an atom only has 1 or 7 valence electrons, it is very reactive (it will readily lose or gain 1 electron to have a full shell). When an atom alreqady has 8 valence electrons it is very stable and non-reactive (it does’t wat to lose or gain electrons).
What is the difference between groups and periods?
- The vertical columns are groups and are labelled 1-18. For main group elements (1-12,13-18) can use group numbers to determine the number of valence electrons.
- The horizontal rows are periods and are labelled 1-7. It tells us how many occupied shells an atom has. E.G: Period 1 = 1 shell, Period 2 = 2 shells, Period 3 = 3 shells, and so on.
What are the main group names and transition metals?
Group 1 (Alkali): Highly reactive metals
Group 17 (Halogens): Highly reactive nonmetals
Group 18 (Noble Gases): Least reactive elements
What is reactivity and what does it mean in terms of metal and non-metals?
Reactivity is an indication of how easily an atom of that element loses or gains electrons.
Metals:
Moving down the group, there is an increasing number of electron shells.
The electrostatic force of attraction between the valence electrons and the nucleus is becoming weaker
Non-Metals:
Non-metals are more reactive moving UP the group
They want to gain electrons (opposite goal of metals)
Closer to nucleus, electron more attracted to atoms with less shells
How do transition metals compare with alkali metals?
Compared to the alkali metals, the transition metals:
- Are harder and stronger. They cannot be cut with a knife
- Are more dense. This means that in a fixed volume of metal there are more atoms of a transition metal than there are of an alkali metal.
- Have higher melting and boiling points - except mercury
What is the difference between cations and anions?
Cations: Metals tend to lose electrons. The loss of negatively charged electrons will produce a positive ion. There are now more protons in the nucleus than surrounding electrons. A positively charged ion is called a cation.
Anions: Non-metals tend to gain electrons. When an atom gains a negatively charged electron, the overall charge of the atom is negative. A negatively charged ion is called an anion. When naming an anion we replace the suffix with “ide”. For example, chlorine atoms become chlorine ions.
What are ionic bonds and lattice structures?
Ionic bonds is a chemical bonds formed when one atoms gives up one or more electrons to another atoms
Lattice structure in solid form, sodium chloride will not conduct electricity. Ions are locked in place in a lattice structure and cannot move. The positive and negative charges balance out (overall no charge).
What are diatomic polyatomic valence structures?
Diatomic molecules are molecules with ONLY 2 atoms.
Polyatomic molecules: Molecules with more than 2 atoms.
What are lone pairs?
Non-bonding electrons are the electrons NOT involved in the covalent bond. Pairs of nonbonding electrons are called lone pairs. E.g. Each chlorine atoms has 6 non-bonding electrons present as 3 lone pairs.
What is VSEPR and the 4 molecular shapes?
- valence shell elcectron pair repulsion
VSEPR is a model theory that predicts molecular shape. It states that negatively charged electron pairs in the OUTER shell of an atom repel each other. This results in electron pairs being arranged AS FAR away from each other as possible.
In VSEPR theory, lone pairs are treated the same way as electron pairs in covalent bonds as they influence the shape of the molecule. But lone pairs are not considered part of the shape.
The 4 molecular shapes are Tetrahedral, pyramidal, V-shaped or bent and Linear
What is electronegativity?
Electronegativity: the ability of an atom to ATTRACT electrons. Electronegativity increases across a period. Electronegativity decreases down a group.
What are polar and non-polar bonds?
Polar bonds: Unequal sharing of electrons. Sometimes non-metals don’t share their electrons. We call this POLAR covalent bond. This occurs when one non-metal is more electronegative (attractive) than the other.
Non-Polar bonds: When there is an equal sharing of electrons, the bond is Nonpolar. (Bonds between atoms of the same element will always be non-polar)
How do you determine the polarity of polyatomic molecules?
When looking at molecules with more than 2 atoms, we only care about the polarity between the bonds but also the shape of the molecule. The general rule for symmetrical molecules is nonpolar. While asymmetrical molecules are polar.
