# 18.1 Periodicity  (Page 8/16)

 Page 8 / 16

## Chemistry end of chapter exercises

How do alkali metals differ from alkaline earth metals in atomic structure and general properties?

The alkali metals all have a single s electron in their outermost shell. In contrast, the alkaline earth metals have a completed s subshell in their outermost shell. In general, the alkali metals react faster and are more reactive than the corresponding alkaline earth metals in the same period.

Why does the reactivity of the alkali metals decrease from cesium to lithium?

Predict the formulas for the nine compounds that may form when each species in column 1 of [link] reacts with each species in column 2.

1 2
Na I
Sr Se
Al O

$\begin{array}{l}\text{Na}+{\text{I}}_{2}\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}\text{2NaI}\\ \text{2Na}+\text{Se}\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}{\text{Na}}_{2}\text{Se}\\ \text{2Na}+{\text{O}}_{2}\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}{\text{Na}}_{2}{\text{O}}_{2}\end{array}$
$\begin{array}{l}\text{Sr}+{\text{I}}_{2}\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}{\text{SrI}}_{2}\\ \text{Sr}+\text{Se}\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}\text{SrSe}\\ \text{2Sr}+{\text{O}}_{2}\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}\text{2SrO}\end{array}$
$\begin{array}{l}\text{2Al}+{\text{3I}}_{2}\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}{\text{2AlI}}_{3}\\ \text{2Al}+\text{3Se}\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}{\text{Al}}_{2}{\text{Se}}_{3}\\ \text{4Al}+{\text{3O}}_{2}\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}{\text{2Al}}_{2}{\text{O}}_{3}\end{array}$

Predict the best choice in each of the following. You may wish to review the chapter on electronic structure for relevant examples.

(a) the most metallic of the elements Al, Be, and Ba

(b) the most covalent of the compounds NaCl, CaCl 2 , and BeCl 2

(c) the lowest first ionization energy among the elements Rb, K, and Li

(d) the smallest among Al, Al + , and Al 3+

(e) the largest among Cs + , Ba 2+ , and Xe

Sodium chloride and strontium chloride are both white solids. How could you distinguish one from the other?

The possible ways of distinguishing between the two include infrared spectroscopy by comparison of known compounds, a flame test that gives the characteristic yellow color for sodium (strontium has a red flame), or comparison of their solubilities in water. At 20 °C, NaCl dissolves to the extent of $\frac{\text{35.7 g}}{\text{100 mL}}$ compared with $\frac{\text{53.8 g}}{\text{100 mL}}$ for SrCl 2 . Heating to 100 °C provides an easy test, since the solubility of NaCl is $\frac{\text{39.12 g}}{\text{100 mL}},$ but that of SrCl 2 is $\frac{\text{100.8 g}}{\text{100 mL}}.$ Density determination on a solid is sometimes difficult, but there is enough difference (2.165 g/mL NaCl and 3.052 g/mL SrCl 2 ) that this method would be viable and perhaps the easiest and least expensive test to perform.

The reaction of quicklime, CaO, with water produces slaked lime, Ca(OH) 2 , which is widely used in the construction industry to make mortar and plaster. The reaction of quicklime and water is highly exothermic:
$\text{CaO}\left(s\right)+{\text{H}}_{2}\text{O}\left(l\right)\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}\text{Ca}{\left(\text{OH}\right)}_{2}\left(s\right)\phantom{\rule{3em}{0ex}}\text{Δ}H=\text{−350 kJ}\phantom{\rule{0.2em}{0ex}}{\text{mol}}^{\text{−1}}$

(a) What is the enthalpy of reaction per gram of quicklime that reacts?

(b) How much heat, in kilojoules, is associated with the production of 1 ton of slaked lime?

Write a balanced equation for the reaction of elemental strontium with each of the following:

(a) oxygen

(b) hydrogen bromide

(c) hydrogen

(d) phosphorus

(e) water

(a) $\text{2Sr}\left(s\right)+{\text{O}}_{2}\left(g\right)\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}\text{2SrO}\left(s\right);$ (b) $\text{Sr}\left(s\right)+\text{2HBr}\left(g\right)\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}{\text{SrBr}}_{2}\left(s\right)+{\text{H}}_{2}\left(g\right);$ (c) $\text{Sr}\left(s\right)+{\text{H}}_{2}\left(g\right)\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}{\text{SrH}}_{2}\left(s\right);$ (d) $\text{6Sr}\left(s\right)+{\text{P}}_{4}\left(s\right)\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}{\text{2Sr}}_{3}{\text{P}}_{2}\left(s\right);$ (e) $\text{Sr}\left(s\right)+{\text{2H}}_{2}\text{O}\left(l\right)\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}\text{Sr}{\left(\text{OH}\right)}_{2}\left(aq\right)+{\text{H}}_{2}\left(g\right)$

How many moles of ionic species are present in 1.0 L of a solution marked 1.0 M mercury(I) nitrate?

What is the mass of fish, in kilograms, that one would have to consume to obtain a fatal dose of mercury, if the fish contains 30 parts per million of mercury by weight? (Assume that all the mercury from the fish ends up as mercury(II) chloride in the body and that a fatal dose is 0.20 g of HgCl 2 .) How many pounds of fish is this?

11 lb

The elements sodium, aluminum, and chlorine are in the same period.

(a) Which has the greatest electronegativity?

(b) Which of the atoms is smallest?

(c) Write the Lewis structure for the simplest covalent compound that can form between aluminum and chlorine.

(d) Will the oxide of each element be acidic, basic, or amphoteric?

Does metallic tin react with HCl?

Yes, tin reacts with hydrochloric acid to produce hydrogen gas.

What is tin pest, also known as tin disease?

Compare the nature of the bonds in PbCl 2 to that of the bonds in PbCl 4 .

In PbCl 2 , the bonding is ionic, as indicated by its melting point of 501 °C. In PbCl 4 , the bonding is covalent, as evidenced by it being an unstable liquid at room temperature.

Is the reaction of rubidium with water more or less vigorous than that of sodium? How does the rate of reaction of magnesium compare?

what is chemistry
chemistry is the branch of science which deal with the composition of matter
SHEDRACK
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weight in mg 1.76 mole of I
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the types of hydrocarbons
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Emmanuel
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Jessica
aliphatic and aromatic hydrocarbons
Osakue
stupid boy Emmanuel
Ohanaka
saturated and unsaturated
Leena
I don't use to see the messages
how can you determine the electronegativity of a compound or in molecules
when u move from left to right in a periodic table the negativity increases
reeza
Are you trying to say that the elctronegativity increases down the group and decreases across the period?
Ohanaka
yes and also increases across the period
reeza
for instance when you look at one group of elements in a periodic table electronegativity decreases when you go across the table electronegativity increases. hydrogen is more electronegative than sodium, potassium of that group. oxygen is more electronegative than carbon.
reeza
i hope we all know that organic compounds have carbon as their back bone
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Osakue
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hanna
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Osakue
5, -2 & -2
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What is an atom?
is a smallest particle of a chemical element that can exist
Osakue
Osakue
it is a substance that cannot be broken down into simpler units by any chemical reaction
An atom is the smallest part of an element dat can take part in chemical reaction.
Idris
an atom is the smallest part of an element that can take part in a chemical reaction nd still retain it chemical properties
Precious
Is the smallest particles of an element that take part in chemical reaction without been change
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what are the branches of an atomic mass
Still waiting for answers for a very long time now
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HCl is the strongest dehydrating agent
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Find the number of calcium atoms present in a sample weighing 2.0*10 raise to the power of -3g