Compounds and Bonding - High School Chemistry

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Question

Which compound has both ionic and covalent bonds?

Answer

In , the nitrogen is bound covalently to the three oxygens, and the complex has an overall of .

Sodium has a charge of , and is ionically bound to the complex.

When put into water, the compound will dissociate into and .

HCl is an ionic compound, while the other answer choices have only covalent bonds.

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Question

Which of the following is not true of covalent bonds?

Answer

Covalent bonds form when two atoms share electrons, caused by an overlap of their orbitals. Each atom has a similar amount of "pull" on the electrons, preventing them from getting too close to one atom or the other and keeping them in the middle. This "pull" is the electronegativity. Atoms in covalent bonds have similar electronegativity values to keep the electrons in the center. When the electronegativities are slightly different, the electrons can lean toward one atom. The result is a polar bond, in which one atom is closer to the electrons (negative) and the other is farther (positive). Most non-metals have very high and very similar electronegativity values, and will readily form covalent bonds.

When the difference in electronegativity, or "pull," is too great, the electrons will be transferred from one atom to the other. The result is an ionic bond, which usually forms between a metal (low electronegativity) and a non-metal (high electronegativity).

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Question

Which of the following describes a covalent bond?

Answer

There are two primary types of intramolecular bonds: ionic bonds and covalent bonds. In an ionic bond, an electron is transferred (donated) from one atom to the other, usually allowing both atoms to satisfy the octet rule. In a covalent bond, electrons are shared between two atoms in order to allow both to satisfy the octet rule. A covalent single bond consists of two shared electrons, while a double bond will consist of four and a triple bond will consist of six.

Covalent bonds usually form between two non-metals. Diatomic gases, CH4, and NaOH are all examples of molecules that contain covalent bonds.

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Question

What is the term for a covalent bond in which electrons are not shared equally?

Answer

A polar covalent bond describes a bond between two atoms that share electrons unequally. This results from a difference in electronegativity between the atoms. This difference is enough to cause a dipole, but not enough to consitute an ionic bond.

A non-polar covalent bond is a bond between two atoms sharing ions equally due to similar electronegativities.

A double bond occurs when four electrons are shared between two atoms.

A coordinate covalent bond refers to a covalent bond in which one atom donates both shared electrons.

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Question

Pauling electronegativity values:

Based on the given electronegativities, which of these bonds would most likely be a nonpolar covalent bond?

Answer

A nonpolar covalent bond occurs when two atoms share electrons equally. This happens when the electronegativities of each atom is relatively close to one another. For example, in water, oxygen is much more electronegative than hydrogen (3.5 and 2.1 respectively), oxygen keeps the electrons closer to its nucleus and results in uneven sharing of the electrons between itself and the two hydrogen atoms. This results in a net dipole in the molecule with the oxygen-end being slightly negative, and the hydrogen-end being slightly positive.

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Question

What intermolecular forces can be found in a molecule of ethene?

Answer

Ethene is an organic molecule composed of two carbon atoms, joined by a double bond, and four hydrogen atoms.

Ethene, like all molecules, exhibits London dispersion forces. This molecule, however, has no net dipole moment, so it will not exhibit dipole-dipole attraction. Also, even though it contains hydrogens, it does not exhibit hydrogen bonding. To exhibit hydrogen bonding, the hydrogen atoms must be attached to more electronegative atoms, namely nitrogen, fluorine, or oxygen. Finally, ionic bonding is only present in ionic compounds, not organic compounds.

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Question

Which of the following molecules cannot participate in hydrogen bonding?

Answer

Hydrogen bonding takes place when a hydrogen atom is attracted to a highly electronegative atom in another molecule. Hydrogen bonding takes place between hydrogen and either nitrogen, oxygen, or fluorine. Carbon has an electronegativity similar to hydrogen's, and will not hydrogen bond with hydrogens in other molecules.

Only molecules with -OH, -FH, or -NH groups can form hydrogen bonds.

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Question

Which of the following cannot participate in hydrogen bonding?

Answer

Hydrogen bonds are intermolecular forces between hydrogens and adjacent molecules. These adjacent molecules must contain either fluorine, oxygen, or nitrogen, the three most electronegative atoms. These electronegative atoms pull electrons away from the bonded hydrogen, giving it a small positive charge and giving themselves a slightly negative charge. When the positive hydrogen of one molecule come close to a negative charge on another, the opposite charges attract and pull the molecules close together to form a hydrogen bond. The hydrogen must be bonded to oxygen (-OH), fluorine (HF), or nitrogen (-NH) to have this charging effect.

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Question

Which of the following intermolecular forces is broken when water is boiled?

Answer

Intermolecular forces are transient forces between two separate molecules. Water is a polar molecule. The oxygen atom carries a slight positive charge, while the hydrogen atoms carry slight negative charges. This is the result of the large difference in electronegativity between oxygen and hydrogen. When two water molecules are next to each other, the partially positive hydrogen will be attracted to the partially negative oxygen. This attraction is known as a hydrogen bond.

Ionic bonds, covalent bonds, and double bonds are all _intra_molecular forces. These are stable bonds between atoms that establish the identity of the molecule. Breaking any of these bonds would alter the identity of the compound.

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Question

Water has a higher boiling point than hydrogen sulfide due to which type of bonding?

Answer

Hydrogen bonding occurs between a hydrogen atom on one molecule and a very electronegative atom—namely oxygen, nitrogen, or fluorine—on a neighboring molecule. This electrostatic force results in a stronger intermolecular bond than would otherwise be present without the hydrogen bond. A stronger intermolecular bond results in a higher boiling point.

Water (H2O) exhibits hydrogen bonding between the hydrogen of one water molecule and the oxygen of another water molecule. Since sulfur is not as electronegative as oxygen, hydrogen sulfide (H2S) does not exhibit hydrogen bonding. This is the reason why water is a liquid at room temperature, while hydrogen sulfide is a gas.

Wrong answers explained: Neither water nor hydrogen sulfide has ionic bonds. Both have covalent bonds and London dispersion force, but this does not explain why water's boiling point is higher. Heisenberg bonding does not exist and is a misleading answer option.

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Question

Which of the following compounds will exhibit hydrogen bonding?

Answer

When hydrogen is bound to either fluorine, oxygen, or nitrogen, the hydrogen atom carries little of the electron density of the covalent bond. This partially positively charged hydrogen atom may interact with the partial negative charge located on adjacent electronegative atoms such as F, N, or O on adjacent molecules. Note that hydrogen bonds are intermolecular forces, not intramolecular. This means that hydrogen bonds form between two separate molecules. They plan an important role in the chemistry of water, and other compounds that exhibit hydrogen bonding.

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Question

Sodium will react with oxygen and form an ionic compound. Which of the following is false concerning this interaction?

Answer

Electronegativity is defined as the tendency of an atom to attract an electron in a bond that it shares with another atom. Because oxygen wants to receive two elctrons, while both sodiums wish to lose one electron, oxygen has a higher electronegativity than sodium. Typically, electronegativity can be seen as increasing as you go to the top right of the periodic table. For example, fluorine has a higher electronegativity than nitrogen.

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Question

Ionic bonds most commonly form between which of the following?

Answer

Ionic bonds most commonly form between metals and non-metals. Non-metals have high electronegativities and metals have low electronegativities. In these type of bonds, electrons are transferred from the metal to the non-metal because of the large difference in electronegativities. The non-metal will try to gain an electron (high electronegativity) and the metal will try to donate an electron (low electronegativity). The result is a complete electron transfer, known as an ionic bond.

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Question

A large difference in which atomic property between two atoms will result in an ionic bond?

Answer

Electronegativity is the tendency of an atom to attract an electron. Elements with very high electronegativities are found at the upper right of the periodic table, while those with low electronegativities are found at the lower left. When two atoms have a very large difference in electronegativity, one atom will have a much greater tendency to attract an electron than the other. As a result, the more electronegative element will pull an electron away from the less electronegative element, creating an electron transfer. This transfer is an ionic bond.

Most non-metals have very high electronegativities, while most metals have very low electronegativities. This is why ionic bonds usually form between a metal atom and a non-metal atom.

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Question

Which of the following describes ionic bonds?

Answer

There are two primary types of intramolecular bonds: ionic bonds and covalent bonds. In an ionic bond, an electron is transferred (donated) from one atom to the other, usually allowing both atoms to satisfy the octet rule. In a covalent bond, electrons are shared between two atoms in order to allow both to satisfy the octet rule.

Ionic bonds usually form between a metal and a non-metal. HCl, NaCl, and NaOH are all examples of molecules that contain ionic bonds.

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Question

Which of the following describes an ionic bond?

Answer

Ionic bonds occur when there is a large electronegativity difference between two atoms, such as elemental between fluorine and potassium. The transfer of one electron will fill the valence electron shell of both atoms. Remember that ionic bonds result in ions, or charged species. A covalent bond is a chemical bond in which two atoms share one or more electrons, but the electron(s) is/are never fully donated or accepted.

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Question

Which of the following molecules has only ionic bonds?

Answer

An ionic bond is a complete transfer of electrons between atoms which forms a cation and an anion. A metal (cation) tends to gain electron(s) and a non-metal tends to lose electron(s). Both act to satisfy their octets and the electrostatic attraction between the oppositely charged atoms holds them together.

Diatomic chlorine forms covalent bonds since they are equal in terms of electronegativities.

forms a polar covalent bond based on the two atom's differing electronegativities, and on the fact that both atoms are nonmetals.

has both ionic bonds (between the metal and polyatomic ion) and covalent bonds within the polyatomic ion. Since we are only looking for ionic bonds, is the correct answer.

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Question

How many lone pairs of electrons exist on the following molecule?

BF3

Answer

.. ..

:F — B — F: Boron can have a violated octet (6 e-) and each F has 3 lone pairs

.. | .. for a total of 9 pairs of unpaired electrons

:F:

..

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Question

Which of the following compounds contains an atom that does NOT satisfy the octet rule?

I.

II.

III.

IV.

Answer

BCl3 only has six electrons around boron, while NO2 (with an odd number of electrons) would have only 7 electrons around the central nitrogen.

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Question

Which of the following compounds breaks the octet rule?

Answer

The octet rule requires that each atom in the molecule has eight valence electrons, fully filling the s and p subshells. Atoms that have a full octet tend to be more stable and lower in energy.

In the compound , each fluorine has seven initial valence electrons and boron has three initial valence electrons. Upon forming the compound bonds, boron shares its three electrons with each fluorine through covalent bonds. This givens each fluorine a full octet, but leave boron with only three covalent bonds, resulting in only six valence electrons. Boron does not satisfy the octet rule in this compound.

Each atom in the other listed compounds forms bonds to generate a full octet. Sodium chloride achieves this through an ionic bond. Methanal and diatomic oxygen both use double bonds to help achieve octets.

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