Which of the following is true about an individual atom? Explain. a. An individual atom should be considered to be a solid. b.An individual atom should be considered to be a liquid. c. An individual atom should be considered to be a gas. d. The state of the atom depends on which element it is. e. An individual atom cannot be considered to be a solid, liquid, or gas. Justify your choice, and for choices you did not pick, explain what is wrong with them.

Mass spectrometric analysis showed that there are four isotopes of an unknown element having the following masses and abundances: Three elements in the periodic table that have atomic weights near these values are lanthanum (La), atomic number 57, atomic weight 138.9055; cerium (Ce), atomic number 58, atomic weight 140.115; and praseodymium (Pr), atomic number 59, atomic weight 140.9076. Using the data above, calculate the atomic weight, and identify the element if possible.

Classify the following as compounds or elements: a silver bromide used in photography; b calcium carbonate limestone; c sodium hydroxide lye; d uranium; e tin; f titanium.

The photo here depicts what happens when a coil of magnesium ribbon and a few calcium chips are placed in water. (a) Based on these observations, what might you expect to see when barium, another Croup 2A element, is placed in water? (b) Give the period in which each element (Mg. Ca, and Ba) is found. What correlation do you think you might find between the reactivity of these elements and their positions in the periodic table?

Write the formulas of the following compounds. (a) ammonia (b) laughing gas (c) hydrogen peroxide (d) sulfur trioxide

An isotope of an element contains 63 protons and 91 neutrons. (a) Identify the element and give its symbol. (b) Give the elements atomic number. (c) Give the mass number of the isotope. (d) This element has two naturally occurring isotopes. Given the information in the table, calculate the atomic weight of the element. (e) In which region of the periodic table is the element found? Explain your answer. (f) Is the element a metal, metalloid, or nonmetal? Explain your answer. (g) This element, used in compact fluorescent light bulbs and computer screens, has an atomic radius of 180 pm. Calculate how long the chain of atoms would be if all the atoms in a 1.25-mg sample of this element were put into a row.

Which elements conduct electricity? a. metals b. nonmetals c. metalloids d. ions

The following isotopes have applications in medicine. Write their symbols in the form XZA. a. cobalt-60 b. phosphorus-32 c. iodine-131 d. sulfur-35

Each of the following statements is true, but Dalton might have had trouble explaining some of them with his atomic theory. Give explanations for the following statements. a. The space-filling models for ethyl alcohol and dimethyl ether are shown below. These two compounds have die same composition by mass (52% carbon, 13% hydrogen, and 35% oxygen), yet the two have different melting points, boiling points, and solubilities in water. b. Burning wood leaves an ash that is only a small fraction of the mass of the original wood. c. Atoms can be broken down into smaller particles. d. One sample of lithium hydride is 87.4% lithium by mass, while another sample of lithium hydride Ls 74.9% lithium by mass. However, the two samples have the same chemical properties.