Chemistry A Final
Why are molecular models important in the understanding of molecules? Select all that apply.
- They provide insight as to how a molecule will interact. - They provide a visual representation of the arrangement of atoms, bonds, and valence electrons in a molecule.
What is true about protons within an atom?
- They are positively charged. - They are equal to the atomic number.
Examine the images. What do the dots in the images represent?
- the locations of electrons in the p orbital; the closer the dots are to each other, the greater probability of finding an electron
Magnesium has 12 electrons. How many valence electrons does magnesium have?
- two valence electrons
How is an ion formed?
- when an atom gains or loses electrons
When are atoms considered stable?
- when they have satisfied the octet rule naturally or through bonding to obtain full valence shells
Neon is highly unreactive. Based on neon's location in the periodic table, what other element would also be highly unreactive?
- xenon
What is the net electric charge of an ionic compound?
- zero
Which answer best describes nonmetals?
- They can be found mostly in Groups 14 to 18 and are often brittle.
Carbon's ground state electron configuration is 1s2 2s2 2p2. What is carbon's excited state configuration?
- 1s2 2s1 2p3
When an atom of oxygen (O) forms an anion by gaining two electrons, what is the anion's charge?
- 2-
What orbitals would be present in principal energy level two?
- 2s, 2p
An iron atom has 26 protons and 30 neutrons. What is the mass number of this atom?
- 56 amu
Examine the table. Based on the information provided for the isotopes of copper (Cu), what is the average atomic mass of copper?
- 63.55 amu
Examine the table. Based on the information provided for the isotopes of strontium (Sr), what is the average atomic mass of strontium?
- 87.62 amu
Which options describe a heterogeneous mixture? Select all that apply.
- A cookie made from flour, eggs, sugar, butter, and chocolate chips. - Cool air mixes with warm moist air, and the mixture condenses to form fog.
How is the crystal lattice of an ionic compound different from the crystal formation of a metallic compound? Select all that apply.
- A metallic compound forms a crystal structure with overlapping valence atomic orbitals and has delocalized electrons that are free to move around. - A metallic compound forms a crystal structure with overlapping valence atomic orbitals and has delocalized electrons that are free to move around. An ionic compound has a rigid crystal structure with positive and negative ions fixed in place based on attractive forces.
Why would an atom prefer to be in a bond than remain as a separate atom?
- A molecule, the result of bonding, has lower energy than separate atoms.
A potassium ion will commonly lose an electron to form an ion. When a potassium (K) ion is formed, what is its charge and why?
- A potassium ion will form a 1+ charge because it will have more protons than electrons.
What is true about metallic bonds?
- A strong metallic bond occurs when more electrons become delocalized from the metal.
Why is an excited atom more likely to react than an atom at ground state if they are both the same element? Select all that apply.
- An atom in the excited state has more unpaired electrons available to bond than an atom in the ground state. - An atom in the excited state is less stable than an atom in the ground state.
What limitations might an atomic model have in properly illustrating the structure of an atom?
- An atomic model can only explain what scientists have observed about the atom and may get updated as new discoveries are made.
If a crystal lattice structure is so hard, what causes most ionic compounds to be brittle?
- Applying force, such as striking the crystal with a hammer, can shift ions, causing ions of similar charges to align, repel each other, and fragment the crystal.
Why might a metallic compound be mistaken for an ionic compound, based on its physical properties?
- Both metallic and ionic compounds can conduct electricity when molten. However, only metallic compounds can conduct electricity in a solid state.
What is one purpose that alkali earth metals serve in our bodies?
- Calcium (Ca) is an important part of our bodies in producing strong bones and teeth.
What model represents Thomson's view of the atom?
- Circle shape, plus in middle, surrounded by negatively charged electrons
Using the electron configuration, how many valence electrons does chlorine (Cl) have? HINT: Chlorine's atomic number is 17.
- Cl: 1s22s22p63s23p5Since there are two electrons in 3s and five electrons in 3p, there are seven valence electrons.
Is density an intensive or extensive physical property?
- Density is considered an intensive property of matter because it does not depend on the amount of matter. As the mass of a substance increases, the volume will also increase proportionally.
How does electronegativity change as principal energy levels are added to an atom?
- Electronegativity decreases.
Moving left to right across the periodic table, what happens to electronegativity?
- Electronegativity increases.
How does the plum-pudding model illustrate the atom's structure? Select all that apply
- Electrons are distributed throughout an atom with a positively charged mass. - Electrons have a negative charge.
What is true about bonds? Select all that apply.
- Forming a bond releases energy. - Breaking a bond requires energy.
Examine the table. Which element has the greatest atomic mass?
- Francium
Why are metals in the first column of the periodic table, like sodium (Na), considered highly reactive?
- Group 1 metals have a large atomic radius compared to other elements and can lose electrons easily.
What are the characteristics of homogeneous mixtures?
- Homogeneous mixtures are evenly distributed and the same throughout.
What is true about an atom in an excited state? Select all that apply.
- It has more energy than a ground state atom. - It is more likely to enter chemical reactions.
Chlorine has an electronegativity of 3.16. Bromine is below chlorine on the periodic table. Iodine is below bromine, and its electronegativity is 2.66. What can be said about bromine's electronegativity?
- It is between 3.16 and 2.66.
Nitrogen has a first ionization energy of 1402 units. Carbon is to the left of nitrogen on the periodic table. What can be said about the first ionization energy of carbon?
- It is lower than 1402 units.
What identifies a flaw in Dalton's model of the atom?
- It showed that atoms are tiny, hard, indivisible spheres with no charge.
What correctly explains a specific characteristic of a physical property of matter?
- Melting point is a physical property of matter because when a substance melts, it changes state from a solid to a liquid but is still the same substance.
Why is melting point considered a physical property?
- Melting point is the temperature at which a substance changes from a solid to a liquid state. It is a physical property because measuring melting point does not change the identity of the substance.
What is a metalloid?
- Metalloids have characteristics of both nonmetals and metals; they can lose electrons easier than nonmetals, but not as well as metals.
What are physical properties of matter?
- Physical properties are characteristics of a substance that can be observed and/or measured without altering the substance's identity.
How did Ernest Rutherford's atomic model compare to the plum-pudding model?
- Rutherford's atomic model was the first to show that the positive charges within an atom are not a uniform charge; rather they are located in a central nucleus.
How do s orbitals differ based on the energy level?
- S orbitals increase in size as they increase in principle energy levels.
How is atomic mass calculated?
- Since the atomic mass is calculated as the sum of protons and neutrons, it is measured in amu. This is because protons and neutrons each have a mass of 1 amu.
An atom contains 27 protons, 32 neutrons, and 27 electrons. What is the element's atomic number and what is the element's mass number?
- The atomic number is 27, and the mass number is 59.
What happens during covalent bonding?
- The attractive and repulsive forces between the atoms are equal and the atoms share electrons.
Why do most metallic compounds have high luster?
- The electrons absorb photons and then emit them back.
What identifies a flaw in J. J. Thomson's model of the atom?
- The plum-pudding model did not identify a central nucleus as the source of a positive charge.
Examine the following isotopes of silicon (Si). silicon-28 (28Si) silicon-29 (29Si) silicon-30 (30Si) What is true about these isotopes?
- They all have the same number of protons but different numbers of neutrons.
How are the three p orbitals in a p sublevel arranged?
- They are all the same size and shape, but each is on a different axis of a three-dimensional coordinate system.
Why are noble gases, like helium and krypton, unlikely to form a bond?
- They have full valence orbitals and already have low energy.
What describes how J. J. Thomson's model of the atom differed from John Dalton's model of the atom?
- Thomson's model showed atoms as a positively charged mass with small negative charges distributed throughout, while Dalton's model showed atoms as spheres with no charge.
How is a metallic compound different from an ionic compound? Select all that apply.
- When hit with a hammer, a metallic compound will change shape, while an ionic compound is likely to break.
Is the boiling point of a substance considered a physical property?
- Yes, boiling point is considered a physical property because when a substance boils, it changes its state of matter but is still the same substance.
Write the electron configuration for barium.
- [xe]6s2 - 1s22s22p63s23p64s23d104p65s24d105p66s2
What is an ionic bond?
- a bond formed through the attraction between oppositely charged ions
What is a mixture?
- a combination of two or more pure substances that can be separated through physical means
What is the general structure of an ionic compound?
- a crystal lattice structure of anions and cations
What is a covalent compound?
- a stable group of more than one type of atom bonded by bonding electron pairs
Why are metallic compounds malleable and ductile?
- because metal atoms share electrons freely between cations, when hammered, the electrons move aside, and the cations slide past each other, allowing the metal to change shape
What are examples of physical properties? Select all that apply.
- boiling point - density
Which elements belong to the halogen family? Select all that apply.
- bromine - fluorine
What family of elements contains silicon, a metalloid important in the electronics industry?
- carbon family
When an atom of calcium (Ca) forms an ion by losing two electrons, what is the ion's type and charge?
- cation, 2+
What are some physical properties of a metal? Select all that apply.
- conducts heat well - malleable - ductile
What is the measure of an atom's ability to attract electrons from other atoms in a compound?
- electronegativity
What represents the amount of energy required to remove just one electron from an atom?
- first ionization energy
Which family of elements on the periodic table is highly reactive and is made up of almost all nonmetals?
- halogens
What are physical properties of ionic compounds? Select all that apply.
- high melting and boiling points - hard and brittle - crystal structure
What most accurately describes the melting point of ionic compounds?
- high melting points
How could you identify that two elements have formed an ionic bond?
- if one element has transferred valence electrons to another element's valence shell, forming a cation and anion
Based on periodic trends, what trend increases going across a period and decreases going down a group?
- ionization energy
Which is a property of a covalent compound?
- low melting point
Study the observations made about a sample of a substance. - silver-colored solid - melts at 420 °C - density of 7.13 g/cm3 - mass of 18.50 g What is an extensive physical property of this material?
- mass of 18.50 g
Many electronic components use what class of elements because of their ability to both gain and lose electrons?
- metalloids
Which class of elements can be described as having good conductors of electricity?
- metals
Which family is the least reactive group of elements?
- noble gases
Oxygen has eight electrons. How many valence electrons does oxygen have?
- six valence electrons
What would the shape of an s orbital look like?
- spherical
What is an atomic radius?
- the distance from the nucleus of an atom to its outermost atomic orbital
What explains the structure of metals and delocalized electrons?
- the electron sea model
What is ionization energy?
- the energy required to remove an electron from an atom
What is the maximum amount of electrons that all d orbitals orientations can hold?
- 10
Refer to images A and B. Which choice identifies the compound's structural formula, and what information does the structural formula provide that the molecular formula does not?
Image B represents the structural formula, and only the structural formula allows the molecular shape to be determined because it shows the position and alignment of the atoms and bonds.
Which elements belong in Group 16 of the periodic table? Select all that apply.
- sulfur - oxygen
Based on electrostatic forces, how would two electrons interact with each other?
- The electrons would repel each other because they have the same charge.
Two hydrogen atoms covalently bond to form a hydrogen molecule. What is true about the hydrogen molecule?
- The hydrogen molecule has less energy than the two atoms.
What is the difference between mass number and atomic number?
- The mass number is the sum of protons and neutrons, while the atomic number is the number of protons.
Examine the image Which options most accurately describe the reactivity of metals? Select all that apply.
- The metals at the bottom of the periodic table are more reactive than metals at the top of the periodic table. - The metals farthest to the left of the periodic table are the most reactive metals.
A student describes a mixture by writing, "It is a colorless liquid with white particles dispersed throughout the liquid. Some white particles have settled on the bottom of the test tube." What type of mixture is the student describing?
- The student is describing a heterogeneous mixture because the mixture is not the same throughout.
What is the arrangement of positive metal ions compared to valence electrons in a metallic bond?
- The valence electrons are free to move between different ions, while the positive metal ions are fixed in place.
What is true about metals?
- Valence electrons of metals are delocalized.
What is a metallic bond?
- an attractive force between delocalized electrons and metal cations
If an atom of gold (Au) contains 79 protons and 118 neutrons, what is its atomic mass?
- 197
What is true about ionic compounds? Select all that apply.
- Properties of the compound are different than the properties of individual atoms that make the compound.
Examine the table. Which element has the greatest atomic mass?
- seaborgium at 263
What is the maximum amount of electrons that one orbital can hold?
- 2
What happens to the atomic radius across groups and periods?
- Atomic radius decreases from left to right across a period and increases down the group.
