Matter Review
1. 1-A physical change does not produce a new substance or change the composition of a substance.
2. 4-Particles in different states of matter exhibit different behaviors and properties.
3. 1-Chemical properties describe how a substance changes into a completely different substance. Flammability is one example.
4. 3-Composition determines the structure of a substance, while the physical properties can be attributed to the number and strength of bonds.
5. 3-When you heat a solid, its temperature rises and then remains constant during the melting process.
6. 2-Chemical reactions that require the absorption of energy to occur are endothermic. Melting (sàl) and evaporation (làg) both require energy to occur.
7. 1-Sublimation is the phase change from solid to gas.
8. 2-Low intermolecular attractions enable the phase change to occur, and gases produce high vapor pressure.
9. 1-A hydrogen bond is the attractive interaction of a hydrogen atom with an electronegative atom (F,O,N). Water has two hydrogen-oxygen bonds, as where HF only has one H-F bond.
10. 2-Of all the answer choices, HI has the weakest IMFs.
11. 3-Use Table H and match temperature with pressure.
12. 2-A compound is a substance whose smallest unit is made up of atoms of more than one element bonded together. A mixture is a combination of two or more substances where there is no chemical combination or reaction.
13. 3- Again, A mixture is a combination of two or more substances where there is no chemical combination or reaction.
14. 1-Different elements have different boiling points.
Atomic Structure
1. 2-The nucleus of an atom is positive; it contains positively-charged protons and neutrally-charged neutrons. The nucleus is surrounded by negatively-charged electrons.
2. 3- The mass of the isotopes and fractional abundance of the isotopes can be used to calculate the atomic weight. Add the mass of each isotope and multiply by its fractional abundance.
3. 3-This is a fact to be memorized and explains why there are attractive forces between protons and electrons.
4. 1- An atomic orbital can hold a maximum of two electrons with opposite spins.
5. 2-The charge of an atom’s nucleus is determined by the number of protons it contains.
6. 1-An excited state of an atom has higher energy than the ground state. An electron must gain energy in order to move to a higher energy level.
7. 1-This is a fact to be memorized. Electrons have a lower mass than protons and neutrons. Neutrons and protons are proximately equal in mass.
8. 1-Sulfur is in the oxygen group; each element in this group has 6 valence electrons.
9. 1-During a chemical change, substances are changed into different substances. Chemical reactions result in the formation or dissociation of molecules.
10. 1-Potassium has nineteen protons (atomic number, as given on reference table). The 42 in an atom of K-42 represents the atomic mass, which is the sum of protons and neutrons. Find the number of neutrons from subtracting the number of protons.
11. 1-An atom of copper has 29 electrons (same number of protons). However, a positive-ion of copper (also known as a cation) contains one less electron.
12. 1-When an electron moves from a higher electron shell, it gains energy. Choice 1 is the only answer that shows movement to a higher shell.
13. 4-It is important to remember that the nucleus is a dense region consisting of protons and neutrons. Since neutrons are neutral, the charge of a nucleus is positive.
14. 4-A potassium ion has a charge of +1, meaning it contains one less electron (18) than an atom of potassium (19). An atom of argon contains the same number of electrons as protons (18—atomic number).
15. 3-An atom of chlorine contains 17 electrons. Its ground state configuration is 2-8-7. However, in the excited state, one electron will go to a higher level. This constitutes the change in configuration to being 2-8-6-1.
16. 3-All isotopes of an element contain the same number of protons (atomic number) but have a different number of neutrons, which constitutes a different mass number.
17. 3- Electrons do not stay in excited states for very long. When they return to their ground states, they emit a photon with the same energy as the one that was absorbed to bring it to the excited state.
18. 1-Again, isotopes contain the same atomic number (number of protons) and have different mass numbers (due to different number of neutrons).
19. 2-Electron dot structures display the number of valence electrons. Aluminum has three valence electrons, and hence three dots.
20. 4-Elements in the same group contain the same number of valence electrons. They have a different number of protons and neutrons and therefore do not share the same atomic or mass number.
Periodic Table
1. 2-Trends are important to remember. The nonmetals are typically located to the right, while metals are located to the left. Therefore, metallic character decreases as you move from left to right across a period.
2. 4- Metalloids are the elements found along the “staircase” that separates metals from nonmetals. This line is drawn from between Boron and Aluminum to the border between Polonium and Astatine. NOTE: Polonium is NOT considered a metalloid; there is enough scientific evidence to prove it to be a metal instead.
3. 4-Electronegativity is the ability of an atom to attract electrons. Electronegativity increases as you move across a period from left to right.
4. 1-MELPS HELPS.
5. 4-Atoms in the same group share common characteristics; the number of valence electrons is one of these similarities.
6. 1-Metals have high electrical conductivity. Of the four answer choices, only Mg is a metal.
7. 2-Unlike MELPS, nonmetals gain electrons and become larger in size. Fluorine is gas at STP and is therefore considered a nonmetal.
8. 1-Noble gasses are found in Group 18 of the periodic table.
9. 4-Ductility is due to metallic bonds, which are predominately found in metals. Ionization energy is the energy needed to remove an electron from a valence shell. Ionization energy generally increases across a row in the periodic table. Valence electrons in metals are not strongly held by the nucleus.
10. 3-The presence of mobile electrons causes electrical conductivity of a metal.
11. 4-The Oxygen-group contains 6 valence electrons. Characteristics given in the question indicate that Element X is a nonmetal and is therefore located further to the right on the periodic table.
12. 4-Elements are arraigned according to the number of protons they have, or their atomic number.
13. 1-The first ionization energy is the energy needed to remove the most loosely held electron from one mole of gaseous atoms to produce one mole of gaseous ions, as illustrated below:
X(g)àX+(g) + e-
14. 1-Each group is a family, and each element in a family are similar in characteristics. Each element in a family possesses the same number of valence electrons (for example—Oxygen group contains 6)
15. 1-As you go down a group, the radius increases because the number of electron shells increases. Metallic character also increases because electrons become easier to lose as the atomic radius increases.
16. 1-Nonmetals have a high IE because they typically want to gain electrons; thus more energy is needed to remove an electron. They generally do not conduct heat or electricity due to their lack of metallic character.
17. 3-Elements in group 13 have a charge of +3. When any element from group 13 forms a compound with Bromine (with a charge of -1), the charges are switched for each element.
18. 2-Opposite of MELPS because chlorine is a nonmetal. Nonmetals gain electrons and become larger, while metals lose electrons and become smaller.
19. 4-Bromine, a nonmetal, has 7 valence electrons. It only needs one more electron to have a complete octet.
20. 2-Elements in the periodic table are grouped on the basis of the number of electrons in the outermost shell. So if it's in group 2 it has two valence electrons in its outer most shell.
21. 1-This question is essentially asking which ion has the lowest number of electrons. A fluorine atom has 9 electrons; an ion of fluorine has 10 (due to the -1 charge which means one electron is gained). Cl- has 18 electrons. Both potassium and calcium ions lose electrons due to their positive charges; K+ has 18 and Ca+2 has 18.
22. 3-Nonmetals are brittle; they cannot be rolled into wires or pounded into sheets.
23. 1- Metalloids are the elements found along the “staircase” that separates metals from nonmetals. This line is drawn from between Boron and Aluminum to the border between Polonium and Astatine.
24. 4-Atomic radius increases as you go down an elemental group and decreases as you go across (left to right) a period.
25. 2- The maximum number of electrons that can occupy a specific energy level can be calculated by using the formula 2n2, where n is the number of the principal energy level.
26. 1-Since Calcium and Magnesium are found in the same group, or family, they share similar properties (including # of valence electrons).
27. 3-Colors of ions are facts to be memorized. In aqueous solution, Nickel II is always green.
28. 4-Noble gases are located in group 18 and have all of their orbitals filled. The key to solving this question is by counting the number of electrons each answer choice has. Since Ar is a noble gas, it can be eliminated. Both sodium and magnesium ions lose electrons; Both Mg+2 and Na+ have 10 (same as noble gas Ne). Sulfur, in its ground state, only has 16 electrons.
29. 4-Greater shielding! As the number of principal energy levels increase, the proton-electron attraction decreases.
30. 3-Since the elements are arraigned in the periodic table according to atomic number and atomic number increases as you go across a period, the number of protons increases. Ar has more protons than Na (18 vs 11, respectively).
Nuclear Chemistry
1. 1-Use reference table (Table O)
2. 3-Use reference table (Table O)
3. 1-Use reference table (Table N)
4. 1-An artificial transmutation occurs when an element is converted into another element by artificial means, by means of bombarding with fundamental particles (such as alpha particles).
5. 1-Use reference table (Table N)
6. 4-In nuclear waste, isotopes with very short half-lives are not the major concern because they will decay to insignificant amounts within a year or two. Isotopes with long half-lifes, however, remain active for much longer.
7. 4-Use reference table (Table N)
8. 1-This is a fact to memorize. Carbon-14 is also used in diagnostic medical procedures.
9. 4-The total atomic mass and total atomic number on either side of the arrow must be equal. Since the atomic mass is the same for Np and Pu, X must have an atomic mass of 0. Since Pu has an atomic number of 94, X must have an atomic number of -1 to equal the atomic number of 93 of Np. Use Table N to determine which particle has an atomic number of -1 and an atomic mass of 0.
10. 1- In a fusion reaction, some reactant mass energy is converted to kinetic energy of the products.
11. 3-Gamma rays have the smallest wavelengths, the highest frequency, and the most energy of any other wave in the electromagnetic spectrum. These factors contribute to its high penetrating power.
12. 2-Based on Table N, the half life of gold-198 is 2.69 days. Therefore, after 2.69 days only ½ the nuclide remains.
13. 3-Use reference table (Table N).
14. 3-Radon-222 must undergo 2 half-lifes to go from 200g to 50g. Based on Table N, the half-life of that nuclide is 3.82 days; multiply that number by 2 and you get choice 3.
15. 3-Nuclear decay involves the emission of a charged particle, photon, or both.
16. 4-Natural transmutation occurs in natural radioactivity where alpha or beta particles are emitted.
17. 3-When an isotope retains only 1/8 of its original radioactive atoms, it has undergone 3 half-lifes. Divide 43 days by three to determine the half-life, and you get approximately 14. Based on Table N, phosphorus-32 has a half-life of 14.28 days.
18. 2-The beta particle (with a negative charge) is attracted to the positive plate.
Chemical Bonding
1. 4-Different molecular structures
2. 2- Stronger intermolecular forces result in higher melting and boiling points.
3. 3-A covalent bond represents a shared electron pair between nuclei. Covalent bonds generally occur between two non-polar molecules.
4. 3-Hydrogen chloride is a polar covalent gas. Whenever a chemical bond is formed, energy is released.
5. 4-Nonpolar molecules are symmetrical with a zero dipole moment. It often helps to draw the Lewis-dot structures of the molecules to determine polarity.
6. 3-Phosphate has a charge of -3. Whenever you write a formula, you switch the charges of the molecules. In this case, this becomes Fe3(PO4)3, but the 3’s can cancel out and the formula becomes: FePO4.
7. 1- Stronger intermolecular forces result in higher melting and boiling points.
8. 3-Ionic bonds typically occur between a metal and nonmetal.
9. 2-Metallic bonds occur in a metal.
10. 4- A covalent bond, which typically occur between two nonpolar molecules, represents a shared electron pair between nuclei.
11. 2- Stronger intermolecular forces result in higher boiling points. The dipole moments increase with the polarity of the H-X bond (the greater the difference in EN between the H and halogen atoms, the stronger the dipole-dipole attractions). In this case, F is the most electronegative halogen.