STEM Ch 2 Online Test

An atom that has gained or lost electrons is called an ion. When an atom gains or loses electrons, it becomes electrically charged. This occurs because the number of protons (positively charged particles) no longer equals the number of electrons (negatively charged particles). The resulting charged atom is called an ion. Ions can be positively charged (if they lose electrons) or negatively charged (if they gain electrons).

In a Bohr diagram, the inner orbital closest to the nucleus can hold a maximum of 2 electrons. This is because the first energy level, or the innermost orbital, can only accommodate 2 electrons. The Bohr model of the atom suggests that electrons occupy specific energy levels or shells, and the first shell can hold a maximum of 2 electrons. As we move further away from the nucleus, the subsequent energy levels can hold more electrons.

On a Bohr diagram, the electrons on the outermost shell are called valence electrons. These electrons are responsible for the chemical behavior of an atom as they participate in bonding with other atoms to form compounds. Valence electrons determine the atom's reactivity and its ability to gain, lose, or share electrons with other atoms. The term "ions" refers to atoms or molecules that have gained or lost electrons, while "isotopes" are atoms of the same element with different numbers of neutrons. "Electronegative" refers to an atom's ability to attract electrons in a chemical bond.

Sucrose has the formula C12H22O11, which means it contains 11 oxygen atoms. The subscript 11 in the formula indicates that there are 11 oxygen atoms in each molecule of sucrose.

Atoms are composed of protons, which carry a positive charge, neutrons, which have no charge, and electrons, which carry a negative charge. Therefore, the correct answer is "All of the above" because all three components are present in an atom.

Surface tension is the property of water that allows it to hold a lot of water drops on a penny. Surface tension is caused by the cohesive forces between water molecules, which create a "skin" on the surface of the water. This skin allows the water to resist external forces, such as gravity, and form droplets with a rounded shape. Due to surface tension, the water molecules on the penny are attracted to each other and form a dome-like shape, allowing the penny to hold a significant number of water drops without spilling over.

Fluorine needs to gain one electron in order to fill its outer shell. This is because fluorine has seven electrons in its outer shell, and in order to achieve a stable electron configuration, it requires a total of eight electrons. By gaining one electron, fluorine will have a full outer shell and become stable.

The atomic mass number of an element represents the total number of protons and neutrons in the nucleus of an atom. Carbon has 6 protons and 6 neutrons, so the atomic mass number of carbon is 12.

When atoms form compounds, their outer orbitals become filled. This is because atoms tend to bond with other atoms in order to achieve a stable electron configuration, typically by filling their outermost energy level with electrons. By doing so, atoms can achieve a more stable and lower energy state, which is why they form compounds.

In a Lewis Dot diagram, each dot represents a valence electron. Sulfur has 6 valence electrons, so we would draw 6 dots around the "S" symbol.

Electrons of an atom orbit the nucleus in various energy levels. This is based on the Bohr model of the atom, which states that electrons exist in specific energy levels or shells around the nucleus. These energy levels are quantized, meaning that electrons can only occupy certain allowed energy states. The electrons move in these orbits and can transition between energy levels by absorbing or emitting photons of specific energies. This explanation is consistent with the current understanding of atomic structure and electron behavior.

A covalent bond is formed when two atoms share a pair of electrons. In this type of bond, the electrons are shared equally between the atoms, resulting in a stable molecule. Unlike ionic bonds, where one atom donates an electron to another, covalent bonds involve a mutual sharing of electrons. Hydrogen bonds are a type of intermolecular force, not a bond formed between atoms. Nonpolar bonds do not involve the sharing of electrons, and instead, the electrons are evenly distributed around the atoms. Therefore, the correct answer is covalent bond.

The atomic number of sulfur is 16, which represents the number of protons in the nucleus of a sulfur atom. When drawing the Bohr diagram for sulfur, the diagram would include 16 protons.

A cation is a positively charged ion that is formed when an atom loses one or more electrons. In the case of Na+, the sodium atom has lost one electron, resulting in a positive charge. This can occur when sodium reacts with another element and transfers its electron to the other atom, such as in the formation of sodium chloride (NaCl). In Na+, the positive charge indicates that it has one less electron than the neutral sodium atom.

Polar molecules, such as water, have both negative and positive poles. This is because the molecule has an uneven distribution of electron density, resulting in a partial negative charge (pole) near the oxygen atom and partial positive charges (poles) near the hydrogen atoms. This polarity allows water molecules to form hydrogen bonds with other polar molecules, giving water its unique properties such as high boiling point, surface tension, and solvent abilities.

A water molecule is polar because its hydrogen and oxygen atoms do not share the electrons equally. This means that the oxygen atom attracts the shared electrons more strongly than the hydrogen atoms, creating a slight negative charge near the oxygen atom and a slight positive charge near the hydrogen atoms. This uneven distribution of charge gives the water molecule polarity, making it capable of forming hydrogen bonds with other polar molecules.

On the Bohr diagram of Sulfur, the drawing would contain 3 orbitals (shells). The Bohr diagram represents the arrangement of electrons in an atom, with each shell representing a different energy level. Sulfur has 16 electrons, and these electrons would fill up the first, second, and third shells in the Bohr diagram. Therefore, the correct answer is 3.

Chlorine has an atomic number of 17, which represents the number of protons in its nucleus. The atomic mass of chlorine is approximately 35.5, which is the sum of its protons and neutrons. Since the atomic number is 17, subtracting it from the atomic mass gives us the number of neutrons, which is 18.

When hydrogen bonds with bromine, the bond between them would be a single bond. A single bond is formed when two atoms share one pair of electrons. In this case, hydrogen and bromine each contribute one electron to form a single covalent bond. A double bond would require four electrons to be shared between the two atoms, which is not the case here. Therefore, the correct answer is single.

The correct answer is MgF2 with Mg having a charge of +2 and Fluorine having a charge each of -1. This is because magnesium (Mg) is a metal and tends to lose two electrons to achieve a stable octet configuration, resulting in a +2 charge. Fluorine (F), on the other hand, is a non-metal and tends to gain one electron to achieve a stable octet configuration, resulting in a -1 charge. Therefore, when magnesium bonds with fluorine, it transfers two electrons to each fluorine atom, resulting in a compound with a formula of MgF2 and charges of +2 for magnesium and -1 for each fluorine atom.

HCl is a covalent compound because it is formed by the sharing of electrons between hydrogen and chlorine atoms. In an ionic compound, electrons are transferred from one atom to another, resulting in the formation of positively and negatively charged ions. However, in the case of HCl, the electrons are shared equally between the hydrogen and chlorine atoms, indicating a covalent bond.

All of the given characteristics of water, including adhesion, capillarity, and cohesion, are a result of hydrogen bonding. Hydrogen bonding occurs between the hydrogen atoms of one water molecule and the oxygen atom of another water molecule. This bonding leads to the attraction between water molecules, allowing them to stick to surfaces (adhesion), rise against gravity in narrow tubes (capillarity), and stick together (cohesion). Therefore, all of the mentioned characteristics are a direct result of hydrogen bonding in water.