Periodic Trends in Chemical & Physical Properties Quiz

Answer: Calcium, Silver, Gold

Before Mendeleev's periodic table, Johann Wolfgang Dobereiner, a German chemist, made the first attempt towards classification of elements according to their properties.
The Law of Triads he formulated arranged similar elements in groups of three - showing that the atomic weight of the middle elements is nearly the arithmetic mean of the other two elements' atomic weights.
Iron, Cobalt and Nickel all have similar values of atomic weight already. The fourth triad not included in the question is Calcium , Strontium and Barium.
Today, we know that Iron, Cobalt and Nickel are consecutive elements in the periodic table; Calcium, Strontium and Barium are in group 2 (Alkaline Earth Metals) ; Lithium, Sodium and Potassium are in Group 1 (Alkali metals) ; Chlorine, Bromine and Iodine are in Group 17. (Halogens)
The triads only applied to a limited number of elements known then, and hence were dismissed as a mere coincidence at that time.

Answer: Valence electrons

The number of total electrons and protons is equal to the atomic number, and hence varies for each element. Some elements do have the same number of neutrons (though thy never belong to the same group) , they are said to be isotones. Elements in the modern long form of the periodic table are arranged by their electronic configuration - hence, for elements in the same group, this means the same number of electrons in the valence shells.

Answer: Chlorine (Group 17)

The ionization energies of elements increase as you across the same period (here, the third period), according to the general trend. This is because the number of protons increase , pulling back the valence electrons further - and hence making it harder to separate an electron.
However, there are exceptions! For example, the ionization energy of phosphorus is higher than that of sulfur. This is due to the fact that phosphorus has half-filled 3p-orbitals, giving the configuration some extra stability.
The first ionization energies of sodium, phosphorus, sulfur and chlorine are 496, 1012, 1000 and 1251 kilojoules per mole respectively.

Answer: Higher atomic number

Initially, classification of elements used to be done on the basis of the atomic weight. But given that the number of electrons is more significant in the determination of chemical and physical properties than the number of neutrons, the modern periodic law is used.
The modern periodic law states that the physical and chemical properties of elements are a periodic function of their atomic numbers. An English physicist, Moseley, determined from his experiments in 1912 that the square root of frequencies of X-rays emitted by an element was directly proportional to its atomic number - forming the basis of the law.
Lustrousness, oxidation states and non-metallic character don't form the basis of the classification of elements - although they still exhibit certain trends in the periodic table.
Nickel and Cobalt are transition metals with atomic numbers 28 and 27 respectively. They show variable oxidation states, since for transition metals, the difference between successive ionization energies are low

Answer: K + F2

It may be noticed that all reactant pairs given here are made up from an alkali metal and a halogen.
The general trend dictates that alkali metals get further reactive as you go down the group, while in the case of halogens, reactivity increases as one goes up a group.

Answer: Aluminium

Amphoteric Oxides can act both as acids and bases.
Sodium makes a basic oxide, while sulfur makes an acidic oxide. Argon doesn't form oxides at all - the only noble gas who does so is xenon.
As one goes across the periodic table, oxides of elements turn from basic to acidic - with the middle elements being amphoteric.
Other elements which form amphoteric oxides are zinc, lead, tin, gallium, indium, scandium, titanium, zirconium, vanadium, chromium, iron, cobalt, copper, silver, gold, germanium, antimony, bismuth, and tellurium.

Answer: atomic/ionic radius

Cations have smaller sizes than the parent atoms. This is because the effective nuclear charge increases due to the loss of electrons, resulting in the outer electrons being pulled further in. This effect, along with the already existing positive charge, increases the ionization energy.
As one goes across the periodic table is that, the atomic sizes reduce and the first ionization energies usually increase.
The cation has 10 electrons, while the atom has 13. Both have 13 protons and, for the stable variant, 14 neutrons.

Answer: Decreases as you go down

Electronegativity is the ability of atoms to attract electrons in a covalent bond.
It decreases down any group, as bonding electrons are furthest from the nucleus and the nuclear attraction is reduced.
Fluorine has the highest electronegativity on the Pauling Scale at 4.0

Answer: High electrical conductivity

The concerned element is Chlorine.
However, identification of the specific element isn't necessary - Electronic configurations ending with ns2 np5 are halogens.
Due to their high electronegativities, halogens are highly reactive. They have low melting points, as they experience weak Van der Waals' attraction between their molecular bonds.
Halogens constitute group 17 in the p-block of the periodic table.

Answer: Lithium

Argon has the largest first ionization energy as it is a noble gas and has a stable electron configuration. However,the Alkali metals Lithium and Potassium ENTER stable electron configurations after losing their first electron - and hence it is harder for them to lose another. The remaining electrons in the Li+ ion are closer to the nucleus, hence it takes more energy for it to lose another electron as compared to K+.
Beryllium, as an alkaline earth metal, has the lowest second ionization energy here.