Unit 1 - Chemical Changes and Structure (Periodicity) Flashcards
What is metallic bonding?
- Outer electrons are delocalised (free to move around).
- There is an electrostatic force of attraction between the positive metal ions and the negative delocalised electrons.
- The delocalised ‘sea of electrons’ is responsible for metal elements being able to conduct electricity.
- Have high melting points and boiling points, are solid at room temperature (apart from mercury), and conduct electricity.
What are covalent molecules?
- Small groups of atoms held together by strong
covalent bonds
inside the molecule and weak intermolecular forces between the molecules. - A covalent bond is a shared pair of electrons electrostatically attracted to the positive nuclei of two non-metal atoms.
- Sharing electrons allows atoms to gain a full outer shell of electrons.
- Have low melting points and boiling points, most likely to be liquid or gas at room temperature, and do not conduct electricity.
What are the molecules with a covalent molecular structure?
Hydrogen (H2), nitrogen (N2), fluorine (F2), oxygen (O2), iodine (I2), chlorine (Cl2), bromine (Br2), phosphorus (P4), sulphur (S8), and fullerenes (C60).
What are covalent networks?
- Large, rigid three-dimensional arrangements of atoms held together by strong covalent bonds.
- Have high melting points and boiling points due to the strong covalent bonds, are solid at room temperature, and do not conduct electricity (apart from graphite).
What are the molecules with a covalent network structure?
Boron, carbon, and silicon.
What are the monatomic elements?
- The group 8/0 elements (noble gases) including helium, neon, and argon.
- Exist as single, unattached particles.
- Stable atoms with full outer energy levels, so do not form molecules with other atoms.
- Have low melting points and boiling points as they are easily separated by overcoming the weak forces of attraction between the atoms.
What is covalent radius?
How large an individual atom is.
What happens to the covalent radius as you go across a period from left to right?
Covalent radius decreases because as the atomic number increases, the number of protons in the nucleus increases. The more protons, the stronger the nuclear charge. The stronger the nuclear charge, the more the outer electrons are attracted closer to the nucleus, making the atom smaller.
What happens to the covalent radius as you go down a group?
Covalent radius increases because the atoms have more fully occupied shells of electrons. These fully occupied shells shield the outer electrons from the nucleus’ charge. More shielding leads to less attraction between the nucleus and the outer electrons, meaning that the outer electrons are not held as tightly which makes the atom larger.
What is the first ionisation energy?
The energy required to remove one mole of electrons from one mole of gaseous atoms.
What happens to the ionisation energy as you go across a period from left to right?
Ionisation energy increases because as the atomic number increases, the number of protons in the nucleus also increases. The more protons, the stronger the nuclear charge. The stronger the nuclear charge, the more the outer electrons are attracted to the nucleus, making the outer electrons harder to remove and increasing ionisation energy.
What happens to the ionisation as you go down a group?
Ionisation energy decreases because the atoms have more fully occupied shells of electrons. These fully occupied shells shield the outer electrons from the nucleus. More shielding leads to less attraction between the nucleus and outer electrons, meaning that the outer electrons are not held as tightly and are easier to remove, decreasing ionisation energy.
What is electronegativity?
A measure of the attraction an atom involved in a bond has for the electrons of the bond (an atom’s pulling power for electrons).
What happens to the electronegativity as you go across a period from left to right?
Electronegativity increases because as the atomic number increases, so too does the number of protons in the nucleus. The more protons, the stronger the nuclear charge. The stronger the nuclear charge, the higher the attraction the bonding electrons have to the nucleus, increasing electronegativity.
What happens to the electronegativity as you go down a group?
Electronegativity decreases because the atoms have more fully occupied shells of electrons. These fully occupied shells of electrons shield the bonding electrons from the nucleus. More shielding leads to less attraction between the nucleus and the bonding electrons, meaning that the bonding electrons are not held as tightly and decreasing electronegativity.
