Topic 4: Ionic + Metallic Bonds, Physical Properties
Define the term 'Metallic Bond'
"The electrostatic attraction between a lattice of positive ions and delocalized (valance) electrons" The atoms share delocalized electrons amongst the lattice of positive ions, which acts as a sort of 'glue', giving metals their definitive structure. As the electrons and positive ions have a strong attraction to each other, metals often have high melting and boiling points (since a lot of energy is required to break that bond).
Define the term 'Ionic Bond'
"The electrostatic attraction between oppositely charged ions (cations and anions)" An ionic bond is an electrostatic attraction between two oppositely charged ions. These always include a cation (a metallic ion), and an anion (a nonmetallic ion). The bond occurs because the cation has an abundance of valence electrons, whilst the anion lacks them. Thus the cation will give away its spare electrons and the anion will receive them. This trade off is what makes the ionic bond.
Explain the electrical conductivity and malleability of metals
Conductivity: Anything with freely moving charged particles will conduct electricity. As metals have a lattice of delocalized electrons and non-moving particles which act as a medium, they are capable of conducting electricity. Malleability: Metals can flex/bend because ions can be moved. The metal won't crack because it just bends with the movement of the ions.
Describe the formation of ions due to electron transfer
Ionic bonding occurs because the metallic atom has an abundance of valence electrons whilst the non-metallic atom lacks enough to obtain a full outer shell. The metallic atom will give away spare electrons and the non-metallic atom will receive them. As the metal loses electrons, the proton to electron ratio is changed, leaving more protons than electrons thus giving the metal a positive charge and making it a cation. Since the non-metal gains electrons, it has more electrons than protons thus leaving it as a negatively charged anion.
Describe the lattice structure of ionic compounds
Ionic bonds are formed from the electrostatic attraction between two or more oppositely charged ions. This cohesion results in crystal lattice patterns emerging to accommodate the least amount of space between the ions, while ensuring repulsion from identically charged ions. The pattern can depend on the size of the ions involved.
Figure out which ions will be formed when elements in Groups 5-7 lose electrons
Ions that form due to elements gaining electrons are always negative (since they then have more negatively charged electrons than positively charged protons). The charge number corresponds to the element group, meaning that Group 5 elements will form -3 ions because they need to gain three electrons in order to have a full valence shell. Group 6 elements will form -2 ions because they need to gain two valence electrons, and Group 7 elements will form -1 ions because they only need to gain one more electron to become stable.
Figure out which ions will be formed when elements in Groups 1-3 lose electrons
Ions that form from elements losing electrons will always be positive (since they then have more positively charged protons than negatively charged electrons). In this case, the charge number corresponds to the element group. Group 1 elements will form +1 ions because they only have a single valence electron which they can lose. Group 2 elements will form +2 ions because they have two valence electrons to lose, and Group 3 elements will form +3 ions because they have three.
State the formula of common polyatomic ions formed by nonmetals in Periods 2 and 3 (Nitrate, Hydroxide, Sulphate, Carbonate, Hydrogen Carbonate, Phosphate, Ammonium ion)
Nitrate: NO3- Hydroxide: OH- Sulphate: SO42- Carbonate: CO32- Hydrogen Carbonate: HCO3- Phosphate: PO43- Ammonium Ion: NH4+
Compare/Explain the properties of substances resulting from different types of bonding
The melting point of ionically bonded substances is extremely high in comparison to covalently bonded substances, and similar to one that are metallically bonded. This is because ionic and metallic bonds take a lot more energy to excite. The boiling points of ionic or metallically bonded substances are similar in they are much higher than covalent bonds. The electrical conductivity of metallically bonded compounds is constant because of the delocalized electron structure. Ionically bonded compounds are only conductive when dissolved in a polar solvent due to the rigid ionic lattice. Covalently bonded substances are not conductive due to their rigid electron structure.
Transition metals can form more than one ion. Why? Give an example.
Transition metals are capable of forming more than one ion because their charges are not fixed. The two exceptions are Ag+ and Zn2+. Example: Iron, as a metal, is electrophobic (doesn't like electrons), which means that it must lose electrons to become stable. As a transition metal, it has different ions: Fe 2+ and Fe 3+.
Predict whether a compound of 2 elements would be ionic from the elements' position in the Periodic table or from their electronegativity values. Use MgCl2 as an example.
With the compound Magnesium Chloride (MgCl2), we can predict that this bond is ionic. Firstly, due to their positions in the periodic table we know that Magnesium is a metal, and Chlorine is a nonmetal. As we know, ionic bonds are formed between a metal and a nonmetal, and elements within ionic bonds have an electronegativity difference of 1.8 or higher. By calculating the difference in electronegativity of Mg and Cl, we see that 3.2 - 1.3 = 1.9 which proves that it is an ionic bond.
