Arrange the following substances in order of decreasing magnitude of lattice energy.
KCl NaF SrO BaO
To arrange the substances in order of decreasing magnitude of lattice energy, we need to consider the charges and sizes of the ions.
Lattice energy is a measure of the strength of the attraction between ions in a crystal lattice. It depends on the charges of the ions and the distance between them.
The general trend for lattice energy is that it increases with increasing ion charges and decreasing ion sizes.
Let's analyze each substance:
1. KCl: Potassium (K+) has a charge of +1, and chloride (Cl-) has a charge of -1. Since potassium and chloride ions are similar in size, the main factor determining the magnitude of the lattice energy is the charge. Thus, KCl has the lowest lattice energy of the four substances.
2. NaF: Sodium (Na+) has a charge of +1, and fluoride (F-) has a charge of -1. Sodium and fluoride ions are also similar in size. Therefore, NaF has a slightly higher lattice energy than KCl because fluoride is smaller than chloride.
3. SrO: Strontium (Sr2+) has a charge of +2, and oxygen (O2-) has a charge of -2. Since strontium and oxygen ions are larger than potassium, sodium, fluoride, and chloride ions, their charges have a greater impact on the lattice energy. The higher charges of Sr2+ and O2- result in a higher lattice energy compared to KCl and NaF.
4. BaO: Barium (Ba2+) has a charge of +2, and oxygen (O2-) has a charge of -2. Like SrO, BaO has higher charges for the ions involved. Therefore, BaO has the highest lattice energy among the four substances.
So, the order of decreasing magnitude of lattice energy is:
BaO > SrO > NaF > KCl
To determine the order of decreasing magnitude of lattice energy for the given substances, we need to compare the charges of the ions and the sizes of the ions in each compound.
The lattice energy is the energy released when one mole of a solid ionic compound is formed from its gaseous ions. It is directly related to the strength of the ionic bonds in the compound, which, in turn, depends on both the charges and the sizes of the ions involved.
Generally, the lattice energy increases with increasing ion charges and decreasing ion sizes. So, we need to compare the charges and sizes of the ions in the given compounds to determine the order.
Let's analyze each compound:
1. KCl:
In KCl, potassium (K) has a charge of +1, and chloride (Cl) has a charge of -1. Both ions have similar sizes, so we can primarily focus on their charges. Since K has a lower charge than the other elements, KCl will have the lowest lattice energy among the given compounds.
2. NaF:
In NaF, sodium (Na) has a charge of +1, and fluoride (F) has a charge of -1. Similar to KCl, the ions in NaF have similar sizes. Therefore, NaF will have slightly higher lattice energy than KCl due to the higher charge of sodium compared to potassium.
3. SrO:
In SrO, strontium (Sr) has a charge of +2, and oxygen (O) has a charge of -2. Compared to the previous compounds, the ions in SrO have larger charges. The larger charge difference leads to stronger ionic bonds and increased lattice energy.
4. BaO:
In BaO, barium (Ba) has a charge of +2, and oxygen (O) has a charge of -2, the same as in SrO. Both Ba and Sr are in the same group (Group 2) of the periodic table and have similar atomic radii. Therefore, the lattice energy of BaO will be similar to that of SrO.
Based on this analysis, the order of decreasing magnitude of lattice energy for the given compounds is:
BaO ≈ SrO > NaF > KCl