Ch. 1 S And P Block Elements (Topic 13.2 And 13.3)

As we move down the group of alkali metals, the ionic radii increase. This is because as we move down the group, there is an increase in the number of electron shells or energy levels. The outermost electrons are further away from the nucleus, resulting in a larger atomic radius. Additionally, the increase in the number of electron shells also leads to increased shielding effect, where inner electrons shield the outer electrons from the attractive force of the nucleus, further increasing the ionic radius. Therefore, the correct answer is increase.

The property of alkali metals to give coloration in the burner flame is utilized in the flame test. This test is used to detect the presence of alkali metals in salts. When the salt is heated in the flame, the metal ions present in the salt emit characteristic colors. Each alkali metal produces a unique color in the flame, allowing for the identification of the metal present. Therefore, the flame test is commonly used in salt analysis to identify and distinguish alkali metals.

The electronegativity value of fluorine is 4. Electronegativity is a measure of an atom's ability to attract electrons towards itself in a chemical bond. Fluorine is the most electronegative element on the periodic table, with an electronegativity value of 4. This means that fluorine has a strong ability to attract electrons towards itself when forming a bond with another atom.

The golden-yellow flame color is shown by sodium (Na). When sodium is heated, it absorbs energy and its electrons become excited. As the electrons return to their ground state, they release energy in the form of light. The specific wavelength of light emitted by sodium corresponds to the golden-yellow color. This phenomenon is utilized in flame tests to identify the presence of sodium in compounds.

Be3N2 is the correct answer because beryllium nitride (Be3N2) is a highly volatile compound. Volatility refers to the tendency of a substance to vaporize or evaporate at a low temperature. In the case of Be3N2, the beryllium and nitrogen atoms are held together by weak bonds, making it easier for the compound to break apart and form a gas. This high volatility makes Be3N2 more likely to exist as a gas rather than a solid at room temperature.

The densities of alkali metals are quite low because they have a large atomic volume, large atomic size, and large atomic radii. These factors contribute to the low packing efficiency of alkali metals, meaning that the atoms are more spread out and occupy a larger space. As a result, the mass of alkali metals is spread out over a larger volume, leading to lower densities.

When metal carbonates are decomposed, carbon dioxide gas is evolved. This is because metal carbonates contain carbon and oxygen atoms bonded together. During decomposition, the heat breaks the bonds between the carbon and oxygen atoms, releasing carbon dioxide gas as a byproduct.

LiNO3 decomposes on heating because lithium nitrate is thermally unstable and breaks down into lithium oxide, nitrogen dioxide, and oxygen gas. This decomposition reaction is exothermic and occurs at a relatively low temperature compared to other alkali metal nitrates.

The formula of barium peroxide is BaO2. This is because the compound contains one barium ion (Ba2+) and two oxygen ions (O2-), resulting in the formula BaO2. The subscript 2 in O2 indicates that there are two oxygen ions present in the compound.

Li is the correct answer because it is the alkali metal that is comparatively harder. Alkali metals are known for being soft and having low hardness, but among them, Li is the hardest. This is due to its smaller atomic radius and higher ionization energy compared to the other alkali metals. These factors contribute to stronger metallic bonding in Li, making it harder than the rest.

Rb (Rubidium) burns with both a red and reddish-violet flame. The color of the flame depends on the temperature and the presence of other elements. At lower temperatures, Rubidium burns with a red flame, while at higher temperatures, it produces a reddish-violet flame.

The correct answer is NaNO2. Sodium nitrite is a compound composed of one sodium atom (Na) and one nitrite ion (NO2-). The chemical formula represents the elements and the ratio of atoms in the compound, and NaNO2 accurately represents the composition of sodium nitrite.

The second ionization energy is greater than the first ionization energy because of increasing nuclear pull. This means that as an electron is removed from an atom, the remaining electrons experience a stronger attraction from the positively charged nucleus. This increased attraction makes it more difficult to remove a second electron, resulting in a higher ionization energy.

The melting and boiling points of alkali metals are very low because of the presence of weak inner atomic bonds in the solid state of the alkali metals. This is because alkali metals have one valence electron, which is loosely held and easily lost. As a result, the metallic bonds between atoms are weak, leading to low melting and boiling points.

HCl is the correct answer because it is commonly used in flame tests. Flame tests are used to identify the presence of certain metal ions in a compound. When a metal ion is heated in the flame, it emits a characteristic color. HCl is often used as the acid to dissolve the compound and provide the metal ion for the flame test. It helps in the dissociation of the metal ion, allowing it to release energy in the form of light when heated.