At $50 ^ { \circ } \mathrm { C }$ the ion-product constant for $H_2O$ has the value $K _ { w } = 5.48 \times 10 ^ { - 14 }$ Based on the change in $K_w$ with temperature, predict whether $\Delta H$ is positive, negative, or zero for the autoionization reaction of water: $2 \mathrm { H } _ { 2 } \mathrm { O } ( l ) \rightleftharpoons \mathrm { H } _ { 3 } \mathrm { O } ^ { + } ( a q ) + \mathrm { OH } ^ { - } ( a q )$

Give the formula of a negative ion that would have the same number of electrons as each of the following positive ions. a. $\mathrm{K}^{+}$ b. $\mathrm{Mg}^{2+}$ c. $\mathrm{Sr}^{2+}$ d. $\mathrm{Cs}^{+}$

Predict:
(a) whether the square-planar complex ion $\left[\mathrm{Cu}(\mathrm{py})_4\right]^{2+}$ is diamagnetic or paramagnetic

How many electrons must an aluminum atom, Z=13, lose to attain a noble gas configuration? Write the symbol for the ion formed.

Write the charge and complete ground-state electron configuration of the monatomic ion most likely to be formed by each:
(c) $\mathrm{Ca}$

$(a)$ An oxygen-$16$ ion with a mass of $2.66 \times 10^{-26} \mathrm{~kg}$ travels at $5.0 \times 10^6 \mathrm{~m} / \mathrm{s}$ perpendicular to a $1.20 \mathrm{~T}$ magnetic field, which makes it move in a circular arc with a $0.231 \mathrm{~m}$ radius. What positive charge is on the ion? $(b)$ What is the ratio of this charge to the charge of an electron? $(c)$ Discuss why the ratio found in $(b)$ should be an integer.

In which of the following diatomic molecules would the bond strength be expected to weaken as an electron is removed to form the positive charged ion?

a. $\mathrm{H}_2$

b. $\mathrm{B}_2$

c. $\mathrm{N}_2$

d. $\mathrm{OF}$

What does the symbol $\mathrm{Li}^*$ represent? F. a lithium isotope G. a lithium atom H. a lithium ion L. a lithium molecule

How many electrons are in (a) an ion of $\mathrm{Sc}^{3+}$ ? (b) a $\mathrm{mol}$ of $\mathrm{Sc}^{3+}$ ? (c) a gram of $\mathrm{Sc}^{3+}$ ?

Name each polyatomic ion.

(a) $\mathrm{IO}^{-}$

(b) $\mathrm{IO}_2^{-}$

(c) $\mathrm{IO}_3^{-}$

(d) $\mathrm{IO}_4{ }^{-}$

Write the complete chemical formula (symbol and charge) for the positive ion present in each of the following ionic compounds.

a. KCl

b. CaS

c. $\text{MgF}_2$

d. $\text{Al}_2\text{S}_3$

In an aqueous solution, which substance yields hydrogen ions as the only positive ion? (1) $\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}$, (2) $\mathrm{CH}_{3} \mathrm{COOH}$, (3) KH, (4) KOH.

Classify the following as a monoatomic cation, monoatomic anion, polyatomic cation, or polyatomic anion.

Hydronium ion, $\mathrm{H}_3 \mathrm{O}^{+}$

(a) An oxygen-16 ion with a mass of $2.66 \times 10^{-26} \mathrm{kg}$ travels at $5.00 \times 10^{6} \mathrm{m} / \mathrm{s}$ perpendicular to a 1.20-T magnetic field, which makes it move in a circular arc with a 0.231-m radius. What positive charge is on the ion? (b) What is the ratio of this charge to the charge of an electron? (c) Discuss why the ratio found in (b) should be an integer.