Review #4 Elements, Atoms, and Ions Copyright Cengage Learning. All rights reserved. 4 1
How many of the currently known elements occur naturally? 1. all of them 2. none of them 3. 110 4. 88 Copyright Cengage Learning. All rights reserved. 4 2
ANSWER Choice #4 is correct. Of the 115 known elements, 88 occur naturally. The others have only been made in laboratories. Copyright Cengage Learning. All rights reserved. 4 3
The two most abundant elements in the earth s crust, although they occur as parts of compounds, are 1. nitrogen and oxygen 2. silicon and oxygen 3. nitrogen and silicon 4. carbon and oxygen Copyright Cengage Learning. All rights reserved. 4 4
ANSWER Choice #2 correctly identifies silicon and oxygen as the two most abundant elements in the earth s crust. They are the major components of silicate minerals, which as a group make up over 90% of the earth s crust. Copyright Cengage Learning. All rights reserved. 4 5
The symbol for the element potassium is: 1. P 2. Sn 3. K 4. Au Copyright Cengage Learning. All rights reserved. 4 6
ANSWER Choice #3, K, is the symbol for potassium and is short for the original name (kalium). P is for phosphorus, while Sn and Au are the symbols for tin and gold respectively. Copyright Cengage Learning. All rights reserved. 4 7
Which of the following is one of the statements that make up Dalton s atomic theory? 1. All atoms contain electrons. 2. All atoms of a given element are identical. 3. Atoms are divisible. 4. Atoms gain and lose electrons in chemical reactions. Copyright Cengage Learning. All rights reserved. 4 8
ANSWER Choice #2 is an important component of Dalton s atomic theory. However, we now know that it is not strictly true if one considers isotopes, which we learn about in Section 4.7. Copyright Cengage Learning. All rights reserved. 4 9
How many of the following statements regarding Dalton s atomic theory are still believed to be true? I. Elements are made of tiny particles called atoms. II. All atoms of a given element are identical. III. A given compound always has the same relative numbers and types of atoms. IV. Atoms are indestructible. 1. 1 2. 2 3. 3 4. 4 Copyright Cengage Learning. All rights reserved. 4 10
ANSWER Choice #2 is the correct answer. Statements I and III are still believed to be true. Statement II is no longer true due to isotopes and ions of the same element. Statement IV is no longer true due to nuclear chemistry. Copyright Cengage Learning. All rights reserved. 4 11
Which of the following does Dalton s atomic theory not address? 1. Hydrogen and oxygen gas combine to form water. 2. H 2 O 2 consists of 16 g of oxygen for every 1 g of hydrogen. 3. The seat you are sitting on is made up of atoms. 4. Hydrogen ignites in an open flame but helium does not. Copyright Cengage Learning. All rights reserved. 4 12
ANSWER Choice #4 is the correct answer. Dalton s atomic theory does not address the reactivity of elements. Copyright Cengage Learning. All rights reserved. 4 13
The pesticide known as DDT paralyzes insects by binding to their nerve cells, leading to uncontrolled firing of the nerves. Before most uses of DDT were banned in the U.S., many insects had developed a resistance to it. Write out the formula for DDT. It contains 14 carbon atoms, 9 hydrogen atoms, and 5 atoms of chlorine. 1. C 14 H 9 Cl 5 2. C 9 H 14 Cl 5 3. C 5 H 9 Cl 14 4. CHCl Copyright Cengage Learning. All rights reserved. 4 14
ANSWER Choice #1, C 14 H 9 Cl 5, is the correct answer. Copyright Cengage Learning. All rights reserved. 4 15
Thomson discovered the electron when experimenting with radioactive elements 1. alpha particles 2. thermometers 3. cathode ray tubes Copyright Cengage Learning. All rights reserved. 4 16
ANSWER Choice #4. The cathode ray tube was used by Thomson to eject a stream of electrons from the cathode to cause gas in a tube to glow. Copyright Cengage Learning. All rights reserved. 4 17
The scientist who used alpha particles to bombard a thin film of gold, and proposed that most of the volume of an atom is empty space because most of the alpha particles went straight through the film is: 1. Rutherford 2. Kelvin 3. Thomson 4. Dalton Copyright Cengage Learning. All rights reserved. 4 18
ANSWER Choice #1, Ernest Rutherford, is correct. He disproved the plum pudding model of the atom and proposed that most of the mass of the atom was in a very tiny and very dense nucleus, while electrons moved through space at a relatively large distance from the nucleus. This model is referred to as the nuclear atom. Copyright Cengage Learning. All rights reserved. 4 19
The chemical properties of a particular element are largely determined by the number of an atom of that element possesses. 1. protons 2. neutrons 3. electrons Copyright Cengage Learning. All rights reserved. 4 20
ANSWER Choice #3 is correct. The protons and neutrons are buried within the atom in the nucleus. The electrons occupy most of the volume of the atom and affect the ways in which atoms interact, or react, with each other. Copyright Cengage Learning. All rights reserved. 4 21
Several different types of chemical instruments make use of an excitation source known as a deuterium lamp. Deuterium, H-2, has neutron(s), whereas the most common isotope of hydrogen, H-1, also known as protium, has neutron(s). 1. 2 ; 1 2. 2 ; 0 3. 1 ; 0 4. 1 ; 2 Copyright Cengage Learning. All rights reserved. 4 22
ANSWER Choice #3 correctly expresses the relationship between atomic number, mass number, and the number of neutrons. Deuterium has a mass number of 2 (1 proton + 1 neutron), while protium has a mass number of 1 (1 proton + 0 neutrons). Copyright Cengage Learning. All rights reserved. 4 23
Lead-210 is used in radioactive dating of sediment cores. The number of protons, electrons, and neutrons in an atom of lead- 210 respectively is variable 1. 82, 82, 128 2. 210, 82, 128 3. 128, 128, 82 Copyright Cengage Learning. All rights reserved. 4 24
ANSWER Choice #2 is correct. Lead has an atomic number of 82; hence every lead atom has 82 protons and electrons. To find the number of neutrons, we subtract the number of protons from the mass number (210), which yields 128 neutrons. Lead-210 has a characteristic common to radioactive isotopes: it is relatively rich in neutrons. Copyright Cengage Learning. All rights reserved. 4 25
A certain isotope X contains 23 protons and 28 neutrons. Determine the mass number of this isotope and identify the element. 1. 51; vanadium (V) 2. 51; antimony (Sb) 3. 5; boron (B) 4. 5; nickel (Ni) Copyright Cengage Learning. All rights reserved. 4 26
ANSWER Choice #1 is the correct answer. The mass number is 51. Mass Number = # protons + # neutrons. Mass Number = 23 + 28 = 51. The element is vanadium. The number of protons determines the identity of the element. Copyright Cengage Learning. All rights reserved. 4 27
The element selenium is interesting in that it is an essential element for human health and yet toxic to both plants and animals at elevated levels. It is a, a member of the period, and adjacent to another toxic element,. 1. metal, oxygen, chlorine 2. nonmetal, fourth, arsenic 3. metalloid, oxygen, phosphorus 4. nonmetal, oxygen, arsenic Copyright Cengage Learning. All rights reserved. 4 28
ANSWER Choice #2 is the correct answer for the element whose symbol is Se. Copyright Cengage Learning. All rights reserved. 4 29
How many of the following is/are true about the element fluorine? I. Fluorine is a halogen. II. Fluorine is in period 2 of the periodic table. III. Fluorine is a nonmetal. IV. Fluorine is in Group 7A. 1. 1 2. 2 3. 3 4. 4 Copyright Cengage Learning. All rights reserved. 4 30
ANSWER Choice #4 is the correct answer. All of the statements are true for fluorine. Copyright Cengage Learning. All rights reserved. 4 31
The element that exists as a solid composed of diatomic molecules at room temperature and pressure is 1. silicon 2. iodine 3. chlorine 4. bromine Copyright Cengage Learning. All rights reserved. 4 32
ANSWER Choice #2, iodine, is a diatomic solid. While silicon is a solid, it is not diatomic. Chlorine and bromine are both halogens like iodine, and thus diatomic, but chlorine is a gas and bromine is a liquid at room temperature and pressure. Copyright Cengage Learning. All rights reserved. 4 33
Positive ions, known as can be formed when a metal atom gives up one or more electrons to a nonmetal, which simultaneously forms a negatively charged. 1. cations, anion 2. anions, cation 3. cations, allotrope 4. isotopes, cation Copyright Cengage Learning. All rights reserved. 4 34
ANSWER Choice #1 accurately describes how metal cations and nonmetal anions form by electron transfer. Copyright Cengage Learning. All rights reserved. 4 35
The periodic table is very helpful in assisting in figuring out the charge an atom is likely to have if it accepts or loses electrons to form an ion. When halogens, as typical nonmetals, electrons, they always form ions with a charge of. 1. give up, 2 2. accept, 1 3. give up, 2+ 4. accept, 2+ Copyright Cengage Learning. All rights reserved. 4 36
ANSWER Choice #2 is correct. Nonmetals tend to accept electrons to form negatively charged anions. Halogen atoms accept 1 electron per atom to form an anion with a charge of 1. Copyright Cengage Learning. All rights reserved. 4 37
An ion with a 3+ charge contains 23 electrons. Which ion is it? 1. Fe 3+ 2. V 3+ 3. Ca 3+ 4. Sc 3+ Copyright Cengage Learning. All rights reserved. 4 38
ANSWER Choice #1 is correct. The 3+ charge on the ion means that the ion has lost 3 electrons, therefore the number of protons is 26 (23+3). The ion is Fe 3+. Copyright Cengage Learning. All rights reserved. 4 39
A certain ion X + contains 54 electrons and 78 neutrons. What is the mass number of this ion? 1. 55 2. 132 3. 133 4. 134 Copyright Cengage Learning. All rights reserved. 4 40
ANSWER Choice #3 is correct. The plus charge in X + means that the ion has lost an electron, therefore the number of protons is 55 (54+1). The ion is Cs + with a mass number of 133 (55+78). Copyright Cengage Learning. All rights reserved. 4 41
When aluminum foil is dropped into liquid bromine the ionic compound aluminum bromide forms. This compound s formula is 1. AlBr 2. AlBr 2 3. AlBr 3 4. Al 3 Br Copyright Cengage Learning. All rights reserved. 4 42
ANSWER Choice #3 provides the correct formula. Note that on the periodic table Al is in Group 3, and hence forms a +3 ion. Bromine, a halogen, forms an anion with a charge of 1. We need three Br to balance the Al 3+ and yield an overall charge of zero for the compound. Copyright Cengage Learning. All rights reserved. 4 43
A compound contains an unknown ion X and has the formula XCl 2. Ion X contains 20 electrons. What is the identity of X? 1. Ti 2+ 2. Sc + 3. Ca 2+ 4. Cr 2+ Copyright Cengage Learning. All rights reserved. 4 44
ANSWER Choice #1 is the correct answer. The charge on the cation must be +2 since there are two Cl s each with a 1 charge (giving an overall charge of 2 for the anion side). The cation can now be represented as X 2+, containing 20 electrons. Therefore, 22 protons must be present to give a charge of +2 (+22p 20e = +2). The element with 22 protons is titanium. Copyright Cengage Learning. All rights reserved. 4 45
A member of the alkaline earth metal family whose most stable ion contains 36 electrons forms a compound with bromine. What is the correct formula for this compound? 1. CaBr 2 2. KrBr 3. RbBr 4. SrBr 2 Copyright Cengage Learning. All rights reserved. 4 46
ANSWER Choice #4 is the correct answer. An element in the alkaline earth metal family (Group 2) forms a +2 charge when forming a compound. Therefore two Br ions will be required to give a net zero charge overall. 38 protons must be present to give a charge of +2 (+38p 36e = +2). The element with 38 protons is strontium. The compound is therefore SrBr 2. Copyright Cengage Learning. All rights reserved. 4 47
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