Explain the following:
a. Why a solid has a definite shape but a liquid does not.
b. Why negative ions are larger than their atoms.
c. How scandium, a transition metal forms an ion with a noble gas structure.
d. How the effective nuclear charge changes as you move from left to right across the periodic table and why?
e. The information that can be obtained from a symbol of an element in the periodic table.
a. Because particles in a solid are held together so closely in fixed positions with strong forces of attraction (bonds) between them. The only movement the solid particles have vibration. Whereas in liquids, particles are held together by weak forces of attraction and this allows particles to move and flow from one part of the liquid to another, hence taking the shape of any container they are in.
b. Negative ions have extra electron(s), hence the outer shell electrons experience less effective nuclear charge due to greater shielding effect and electron-electron repulsions that make the ion tend to bulge outwards to accommodate the extra electrons. The ion then becomes relatively larger compared to corresponding atoms.
c. Scandium is atomic number 21
Its electron configuration is [Ar]3d14s2
To form an ion and therefore attain the noble gas (Ar) electronic configuration, the atom has to lose 3 electrons and hence get a +3 oxidation state.
Sc Sc3+ + 3e-
d. Effective nuclear charge is related to the number of protons in the nucleus of an atom. Effective nuclear charge increases from left to right across any period due to an increase in the number of protons in the nucleus.
e. The symbol of an element tells us the name of the element in English or Latin.
It is usually denoted as abZ in the periodic table, where Z is the symbol of the element, a is the mass number, and b the atomic number of the atom.