Chapter Questions
The atomic number of an elementa. equals the number of neutrons in an atom.b. equals the number of protons in an atom.c. equals the number of protons minus the number of neutrons.d. equals the number of neutrons plus the number of protons.e. depends on the isotope.
The mass number of an elementa. equals the number of neutrons in an atom.b. equals the number of protons in an atom.c. equals the number of electrons in an atom.d. equals the number of neutrons plus the number of protons.e. depends on the relative abundances of its electrons and neutrons.
Which of the following statements about the isotopes of an element is not true?a. They all have the same atomic number.b. They all have the same number of protons.c. They all have the same number of neutrons.d. They all have the same number of electrons.e. They all have identical chemical properties.
Which of the following statements about covalent bonds is not true?a. A covalent bond is stronger than a hydrogen bond.b. A covalent bond can form between atoms of the same element.c. Only a single covalent bond can form between two atoms.d. A covalent bond results from the sharing of electrons by two atoms.e. A covalent bond can form between atoms of different elements.
Which of the following statements about water is not true?a. It releases a large amount of heat when changing from liquid into vapor.b. Its solid form is less dense than its liquid form.c. It is the most effective solvent for polar molecules.d. It is typically the most abundant substance in a living organism.e. It takes part in some important chemical reactions.
The reaction $\mathrm{HCl} \rightarrow \mathrm{H}^{+}+\mathrm{Cl}^{-}$ in the humanstomach is an example of thea. cleavage of a hydrophobic bond.b. formation of a hydrogen bond.c. elevation of the $\mathrm{pH}$ of the stomach.d. formation of ions by dissociation of an acid.e. formation of polar covalent bonds.
Using the information in the periodic table (Figure 2.2 ), draw a Bohr model (see Figures 2.5 and 2.7 ) of silicon dioxide, showing electrons shared in covalent bonds.
Compare a covalent bond between two hydrogen atoms with a hydrogen bond between a hydrogen and an oxygen atom, with regard to the electrons involved, the role of polarity, and the strength of the bond.
Use Tables 2.2 and 2.3 to determine for each of the pairs of bonded atoms below:a. whether the bond is polar or nonpolar;b. if polar, which end is $\delta$; andc. whether the bond is hydrophilic or hydrophobic. $$\mathrm{C}-\mathrm{H} \quad \mathrm{C}=\mathrm{O} \quad \mathrm{O}-\mathrm{P} \quad \mathrm{C}-\mathrm{C}$$
Geckos are lizards that are amazing climbers. A gecko can climb up a glass surface and stick to it with a single toe. Professor Kellar Autumn at Lewis and Clark College and his students and collaborators have shown that each toe of a gecko has millions of micrometer-sized hairs, and that each hair splits into hundreds of 200 -nanometer tips that provide intimate contact with a surface. Careful measurements show that a million of these tips could easily support the animal, but it has far more. The toes stick well on hydrophilic and hydrophobic surfaces. Bending the hairs allows the gecko to detach. What kind of noncovalent force is involved in gecko sticking?
Would you expect the elemental composition of Earth's crust to be the same as that of the human body?