Chemistry Practice Midterm Part 2

Atomic number is always the smallest whole number in the symbol and represents the number of protons.

Law of Conservation of Mass states that matter is neither created nor destroyed and is conserved in a chemical reaction.

Observation, hypothesis, experiment and conclusion are all a part of the scientific method. You should know what they mean for the exam.

Group 1=alkali metals, Group 2= alkaline earth metals, Group 17= halogens, Group 18= noble gases.

Atomic number = # of protons and in a neutral atom this will also be the number of electrons. Mass number = protons + neutrons. Mass number - atomic number = # of neutrons.

The dual nature of light is the particle and wave nature that light. All characteristics of waves are considered examples. Wavelength allows us to see color. Speed and amplitude are also wave examples. The particle nature of light examples would include the photon and the photoelectric effect.

Mass number is the number of protons + neutrons and is a whole number. Atomic mass is not a whole number because it is an average of naturally occurring isotopes.

Isotopes have the same number of protons but different number of neutrons and therefore have a different mass number.

Speed is how fast the wave is going and wavelength is a full cycle of a wave pattern (crest to crest or trough to trough).

Electronegativity is the measure of the attraction of electrons. Fluorine is the most electronegative element because it has only 7 valence electrons and a low number of energy levels. The periodic trend for electronegativity will increase towards fluorine.

Elements are the simplest form of a pure substance and a compound is the chemical combination of these. Both are considered pure substances and not mixtures.

You can determine the number of valence electrons an atom has by looking at its group number. Sulfur is in group 16 and therefore has 6 valence electrons.

S block is to the left, d block in the middle, p block to the right and f block below.

The highest energy level listed is 4; therefore the element has to be in the 4th row on the periodic table. 3d5 tells us that it has 5 electrons in the 3rd d energy level (which is in the 4th row).

Cu-63 and Cu-65 are isotopes. 63 and 65 are mass numbers. (65% of 63) + (35% of 65) = 63.7 amu

Sulfur is in the 3rd energy level and has 4 electrons in the p block.

The Law of Conservation of Mass states that the total mass of the reactants (hydrogen gas and oxygen gas) must equal the total mass of the products. 80 g - 8.8 g = 71.2 g. With sig figs, 71.2 g is reduced to 71. g.

The periodic trend for ionization energy is the same as electronegativity. It increases as you move across left to right because the energy to remove a valence electron will increase as the elements acquire more electrons. The trend decreases going down the periodic table because as energy levels are added to the atom, the nucleus has a lesser hold on the valence electrons.

Density = mass/volume. The volume of the piece of metal = 13.5 ml - 10.0 ml = 3.5 ml. Density = 2.0g/3.5 ml.

Use E=hv to find energy. Multiply Planck's constant by the given frequency.

Ionization energy is the energy required to remove an electron from an atom or ion. It is a measure of the strength of the attraction between the electron and the nucleus of the atom. The higher the ionization energy, the more difficult it is to remove an electron. Therefore, the correct answer is "The energy that it takes to remove an electron."

The f sublevel has 7 orbitals and can hold a total of 14 electrons. 2 electrons per orbital.

Dalton stated that matter was rearranged in chemical reactions but not destroyed or created. This is the basis of the Law of Conservation of Mass. You should know about Dalton's Atomic Theory for the test.

Negative ions are larger than neutral atoms due to the electromagnetic repulsion of the valence electrons. Also, the trend in atomic radius increases as it moves down the periodic table due to the added layers of energy levels.

Percent by Mass = (mass of element)/(mass of compound) x 100%. In this case, 50 grams of water - 5.5 grams of hydrogen = 44.5 grams of oxygen. (44.5 g /50. g) x 100% = 89%

Atomic emission spectra are caused by the energy released when electrons jump to a lower energy level or ground state. This energy release corresponds to specific wavelengths of light, which can be used to identify elements. The energy released is in the form of multiples of quanta, known as photons. Therefore, the statement "It is caused by the energy absorbed when electrons jump to ground state" is not true.

Periodic Law states that there is a repetition of physical and chemical properties when elements are listed in atomic number order. The repetition of the number of valence electrons causes this.

Alpha decay is a helium nucleus and has 2 protons and 2 neutrons. When an element goes through alpha decay the element loses 2 protons and 4 mass units. U would go from 92 protons to 90 protons (Th) and from 238 mass units to 234 amu.

1.0 liter = 1000ml. (1000ml/1) x (1 marble/1.3ml) = 769 marbles. (769 marbles/1) x (3.5 grams/1 marble) = 2692 grams. 2692 grams = 2.7 kg.

Metals are shiny, conductive, malleable and ductile. Nonmetals are gases, liquids or dull, brittle solids. Metalloids share these characteristics.

Metals are located to the left of the staircase, which includes the s,d and f blocks. The p block is split between metals and nonmetals at the staircase.

The stairstep on the periodic table separates metals and nonmetals. Not all metals are solids and not all nonmetals are gases.

nm = 1 x 10^-9.

The 4th energy level has 4 sublevels (spdf). The s sublevel holds 2 e-, p holds 6 e-, d holds 10 e- and f holds 14 e- for a total of 32 e- in the 4th energy level.

Use c= (wavelength) v. Convert your wavelength of 440. nm to 4.40 x 10^-7 m. Divide the speed of light (3.00 x 10^8 m/s) by the wavelength.

You need to use both equations. Start with the E=hv and solve for v (frequency). Use frequency (7.55 x 10^14 Hz) in c = (wavelength)v to solve for wavelength. Answer will be in meters. Convert 3.98 x 10^-7 to nm.