Chemistry: Atoms and Elements
Carbon-14, present within living organisms and substances derived from living organisms, is often used to establish the age of fossils and artifacts. Determine the number of protons and neutrons in a carbon-14 isotope.
# of protons = 6, # of neutrons = 8.
An element has two naturally occurring isotopes. Isotope 1 has a mass of 120.9042 amu and a relative abundance of 57.4%, and isotope 2 has a mass of 122.9042 amu and a relative abundance of 42.6%. Find the atomic mass of this element and, referring to the periodic table, identify it.
121.8 amu, Sb (Antimony)
Europium has two naturally occurring isotopes: Eu-151 with a mass of 150.9198 amu and a natural abundance of 47.8%, and Eu-153. Use the atomic mass of Europium to find the mass and natural abundance of Eu-153.
153 amu, 52.2% Natural abundance
What mass of electrons is required to neutralize the charge of 1.0g of protons?
5.4X10^-4g.
Electrical charge is sometimes reported in coulombs (C). On this scale, 1 electron has a charge of -1.6X10^-19 C. Suppose your body acquires -125 mC (millicoulombs) of charge on a dry day. How many excess electrons has it acquired? (HINT: Use the charge of an electron in coulombs as a conversion factor between charge and electrons.)
7.8X10C^17 electrons
Rubidium has two naturally occurring isotopes: Rb-85 with mass 84.9118 amu and a natural abundance of 27.83%. Calculate the atomic mass of rubidium.
85.47 amu
Which elements are main-group elements? A) Te B) K C) V D) Re E) Ag
A & B.
What is a chemical symbol?
A unique, one- or two-letter abbreviation for an element. It is listed below the atomic number for that element on the periodic table.
Determine the number of protons and electrons in each ion. A) Na+ B) Ba2+ C) O2- D) Co3+
A) 11 protons, 10 electrons. B) 56 protons, 54 electrons. C) 8 protons, 10 electrons. D) 27 protons, 24 electrons.
Determine the charge of each ion. A) Oxygen ion with 10 electrons B) Aluminum ion with 10 electrons C) Titanium ion with 18 electrons D) Iodine ion with 54 electrons
A) 2- B) 3+ C) 4+ D) 1-
Bromine had two naturally occurring isotopes (Br-79 and Br-81) and an atomic mass of 79.904 amu. A) If the natural abundance of Br-79 is 50.69%, what is the natural abundance of Br-81? B) If the mass of Br-81 is 80.9163 amu, what is the mass of Br-79?
A) 49.31% B) 78.91 amu
To which group number does each element belong? A) Oxygen B) Aluminum C) Silicon D) Tin E) Phosphorous
A) 6A B) 3A C) 4A D) 4A E) 5A
How many protons are in the nucleus of an atom of each element? A) Ar B) Sn C) Xe D) O E) Tl
A) Argon - 18 B) Tin - 50 C) Xenon - 54 D) Oxygen - 8 E) Thallium - 81
Determine the atomic number and mass number for each isotope. A) The hydrogen isotope with 2 neutrons. B) The chromium isotope with 28 neutrons. C) The calcium isotope with 22 neutrons. D) The tantalum isotope with 109 neutrons.
A) Atomic number 1, Mass number 3 B) Atomic number 24, Mass number 52 C) Atomic number 20, Mass number 42 D) Atomic number 73, Mass number 182
List the symbol and atomic number of each element. A) Carbon B) Nitrogen C) Sodium D) Potassium E) Copper
A) C - 6 B) N - 7 C) Na - 11 D) K - 19 E) Cu - 29
Which statements are INCONSISTENT with Dalton's atomic theory as it was originally stated? Explain your answers. A) All carbon atoms are identical. B) Helium atoms can be split into two hydrogen atoms. C) An oxygen atom combines with 1.5 hydrogen atoms to form water molecules. D) Two oxygen atoms combine with a carbon atom to form carbon dioxide molecules.
A) Correct. B) False - different elements contain different types of atoms according to Dalton. C) False - one cannot have 1.5 hydrogen atoms; combinations must be in simple, whole-number ratios. D) Correct.
Which statements are INCONSISTENT with Rutherford's nuclear theory as it was originally stated? Explain your answers. A) Helium atoms have two protons in the nucleus and two electrons outside the nucleus. B) Most of the volume of hydrogen atoms is due to the nucleus. C) Aluminum atoms have 13 protons in the nucleus and 22 electrons outside the nucleus. D) The majority of the mass of nitrogen atoms is due to their 7 electrons.
A) Correct. B) False - most of the volume of hydrogen atoms is due to the empty space outside the nucleus filled with electrons. C) False - atoms have equal numbers of protons in the nucleus as electrons outside of the nucleus. D) False - the majority of the mass of nitrogen atoms is due to the protons in the nucleus.
Determine whether each statement is true or false. If false, correct it. A) The Ti2+ ion contains 22 protons and 24 electrons. B) The I- ion contains 53 protons and 54 electrons. C) The Mg2+ ion contains 14 protons and 12 electrons. D) The O2- ion contains 8 protons and 10 electrons.
A) False - 22 protons, and 20 electrons. B) True. C) False - 12 protons, and 10 electrons. D) True.
Find the atomic number (Z) for each element. A) Fr B) Kr C) Pa D) Ge E) Al
A) Francium - 87 B) Krypton - 36 C) Protactinium - 91 D) Germanium - 32 E) Aluminum - 13
Classify each element as a halogen, a noble gas, or neither. A) Cl B) Kr C) F D) Ga E) He
A) Halogen B) Noble Gas C) Halogen D) Neither E) Noble Gas
Predict how many electrons each element will most likely gain or lose. A) Ga B) Li C) Br D) S
A) Lose 3, (3+ charge) B) Lose 1, (1+ charge) C) Gain 1, (1- charge) D) Gain 2, (2- charge)
List the name and atomic number for each element. A) Mn B) Ag C) Au D) Pb E) S
A) Manganese - 25 B) Silver - 47 C) Gold - 79 D) Lead - 82 E) Sulfur - 16
Classify each as a metal, nonmetal, or metalloid. A) Sr B) Mg C) F D) N E) As
A) Metal B) Metal C) Nonmetal D) Nonmetal E) Metalloid
Predict the ion formed by each element. A) Rb B) K C) Al D) O
A) Rb+ B) K+ C) Al3+ D) O2-
Complete each ionization equation A) Na ---> Na+ + B) O + 2e- ---> C) Ca ---> Ca2+ + D) Cl + e- --->
A) e- B) O2- C) 2e- D) Cl-
Locate each group on the periodic table and list the charge of the ions it tends to form. A) Group 1A B) Group 2A C) Group 3A D) Group 6A E) Group 7A
A) ion charge = 1+ B) ion charge = 2+ C) ion charge = 3+ D) ion charge = 2- E) ion charge = 1-
Which statements about electrons are true? A) Electrons repel each other. B) Electrons are attracted to protons. C) Some electrons have a charge of 1- and some have no charge. D) Electrons are much lighter than neutrons.
A, B, & D.
Which elements would you expect to lose electrons in chemical changes? A) Potassium B) Sulfur C) Fluorine D) Barium E) Copper
A, D, E.
What is an ion?
An ion is an atom or a group of atoms that has lost or gained electrons and has become charged.
How many electrons would it take to equal the mass of a proton?
Approximately 1.8X10^3 electrons.
Which statements about protons are true? A) Protons have twice the mass of neutrons. B) Protons have the same magnitude of charge as electrons, but are opposite in sign. C) Most atoms have more protons than electrons. D) Protons have a charge of 1+.
B & D.
Which elements are alkali metals? A) Barium B) Sodium C) Gold D) Tin E) Rubidium
B & E.
Which pair of elements do you expect to be most similar? Why? A) Si and P B) Cl and F C) Na and Mg D) Mo and Sn E) N and Ni
B - Chlorine and Fluorine, because they are both in the same group or family.
Which element do you expect to be most like sulfur? Why? A) Nitrogen B) Oxygen C) Fluorine D) Lithium E) Potassium
B - Oxygen, because they are in the same group or family.
Which elements are alkaline earth metals? A) Sodium B) Aluminum C) Calcium D) Barium E) Lithium
C & D.
Which element is a main-group nonmetal? A) K B) Fe C) Sn D) S
D.
What is a family or group of elements?
Each column within the main group elements in the periodic table is labeled as a family or group of elements. The elements within a group usually have similar chemical properties.
What notations are commonly used to specify isotopes? What do each of the numbers in these symbols mean?
Isotopes are noted in this manner A^Z(sub)X. X represents the chemical symbol, A represents the mass number, and Z represents the atomic number.
What was Dmitri Mendeleev's main contribution to our modern understanding of chemistry?
Medeleev noticed that many patterns were evident when elements were organized by increasing mass - from which he formulated the periodic law. From this law, he organized the periodic table and created the basis for the periodic table being used today.
What are the properties of nonmetals? Where are nonmetals found on the periodic table?
Nonmetals have varied properties (solid, liquid, or gas at room temperature). However, as a whole they tend to be poor conductors of heat and electricity, and they all tend to gain electrons when they undergo chemical changes. They are located on the upper-right side of the periodic table.
List the three subatomic particles and their properties.
Proton mass: 1.67262X10^-27kg OR 1 amu charge: +1 Neutron mass: 1.67493X10^-27kg OR 1 amu charge: 0 Electron mass: 0.00091X10^-27kg OR 0.00055 amu charge: -1
Describe Rutherford's gold foil experiment and the results of that experiment. How did these results refute the plum pudding model of the atom?
Rutherford's gold foil experiment involved sending positively charged alpha particles through a thin sheet of gold foil and detecting if there was any deflection of the particles. He found that most passed straight through, but some particles showed some deflection. This contradicted the plum pudding model because the plum pudding model does not explain the deflection of the alpha particles.
If atoms are mostly empty space and atoms compose all ordinary matter, why does solid matter seem to have no space within it?
Solid matter seems to have no empty space within it because electromagnetic forces hold the atoms in a tight arrangement and the variation in density is TOO small to perceive with our eyes.
What is the percent natural abundance of isotopes?
The percent natural abundance of isotopes is the relative amount of each different isotope in a naturally occurring sample of a given element.
How is the periodic table organized?
The periodic table is organized by listing the elements in order of increasing atomic number
What did Democritus contribute to our modern understanding of matter?
The theory that matter was ultimately composed of small, indivisible particles called atoms. Upon dividing matter, one would find tiny, indestructible atoms.
Is matter usually charge-neutral? How would matter be different if it were not charge-neutral?
Yes. If matter was not normally charge-neutral, many unnatural things would occur, such as objects repelling or attracting each other.
