Chem Chapter 2

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Questions and Answers

Which of the following properties distinguishes metals from nonmetals?

Conductivity (correct)

Density

Color

Melting Point

What characterizes nonmetals on the periodic table?

They are found on the left side.

They tend to form anions. (correct)

They tend to form cations.

They have high melting points.

In which family of the periodic table would you find elements that react violently with water?

Transition Metals

Noble Gases

Halogens

Alkali Metals (correct)

Which of the following statements regarding ionic and molecular compounds is false?

Ionic compounds are formed by electron sharing. Signup and view all the answers

What does the molecular mass of a compound represent?

Sum of the atomic masses of all atoms Signup and view all the answers

How do elements in the same group of the periodic table compare to each other?

They have the same number of valence electrons. Signup and view all the answers

Which of the following statements about the states of matter is incorrect?

Gases have a definite volume but not a definite shape. Signup and view all the answers

What is the primary role of neutrons in the nucleus of an atom?

To contribute to the atomic mass without affecting the charge. Signup and view all the answers

Which of the following statements about isotopes is incorrect?

Changes in neutron number affect the chemical properties of an element. Signup and view all the answers

Which of the following properties is typically associated with metals?

Malleability, ductility, and high thermal conductivity. Signup and view all the answers

What defines the charge of an ion?

The balance between the number of protons and electrons. Signup and view all the answers

What is the primary role of neutrons in an atomic nucleus?

To help hold protons together by counteracting their repulsive forces. Signup and view all the answers

What trend occurs in the periodic table as you move from left to right across a period?

Atomic radius decreases and ionization energy increases. Signup and view all the answers

Which of the following represents an isotope of Carbon?

Carbon-11 Signup and view all the answers

How is the average atomic mass of an element determined?

As a weighted average based on the natural abundance of the isotopes. Signup and view all the answers

What defines the atomic number of an element?

The total number of protons in an atom's nucleus. Signup and view all the answers

Which statement accurately describes cations?

They are positively charged ions formed when atoms lose electrons. Signup and view all the answers

What characteristic of metals influences their tendency to form cations?

Their low ionization energy. Signup and view all the answers

Which of the following ions is an example of a polyatomic ion?

OH- Signup and view all the answers

What is typically true about the location of metals on the periodic table in relation to their charge?

They often form cations and are located on the left side and center. Signup and view all the answers

Which of the following correctly describes the relationship between atomic mass and isotopes?

Atomic mass is determined by the average of the isotopes with appropriate weights based on their natural abundance. Signup and view all the answers

Which element could likely have an atomic number of 12?

Magnesium Signup and view all the answers

What did Dalton's atomic theory propose about the nature of matter?

Matter is composed of indivisible particles called atoms. Signup and view all the answers

What does Thomson's Plum Pudding Model represent regarding atomic structure?

Atoms contain both positive and negative charges uniformly distributed. Signup and view all the answers

What was a significant conclusion from Rutherford's Gold Foil Experiment?

Atoms have a small, dense nucleus at the center. Signup and view all the answers

How are protons and electrons characterized in terms of their charges?

Protons have a positive charge and electrons have a negative charge. Signup and view all the answers

Which of the following best describes the role of electrons in an atom?

They are responsible for balancing the atom's positive charge. Signup and view all the answers

What is the primary distinguishing feature of isotopes of the same element?

Different numbers of neutrons Signup and view all the answers

Which notation correctly represents Carbon-14 using hyphen form?

C-14 Signup and view all the answers

How is average atomic mass primarily calculated?

By weighing isotopes according to their natural abundance Signup and view all the answers

What charge does a sodium ion carry after losing one electron?

+1 Signup and view all the answers

Which of the following best describes polyatomic ions?

Ions made up of two or more atoms Signup and view all the answers

Which atomic particle is responsible for the repulsive force within the nucleus?

Protons Signup and view all the answers

What is true regarding the charge of most metals on the periodic table?

They tend to form cations Signup and view all the answers

Which of the following statements about atomic mass is correct?

Atomic mass is the sum of the number of protons and neutrons. Signup and view all the answers

What is a characteristic of ionic compounds?

They form through the attraction between oppositely charged ions. Signup and view all the answers

Which statement accurately describes a key difference between metals and nonmetals?

Metals are good conductors of heat and electricity, nonmetals are poor conductors. Signup and view all the answers

How are elements organized into groups on the periodic table?

By the number of valence electrons. Signup and view all the answers

What does a molecular formula indicate?

The specific ratio of each type of atom in a compound. Signup and view all the answers

Which of the following is a property of solid matter?

It has a fixed shape and fixed volume. Signup and view all the answers

What determines the molecular weight of a compound?

The sum of the atomic masses of all the atoms in the molecule. Signup and view all the answers

Which of the following statements about periods in the periodic table is true?

Elements across a period change their properties systematically. Signup and view all the answers

What significant feature of the atomic structure did Rutherford's Gold Foil Experiment reveal?

The nucleus is a dense center that contains positively charged particles. Signup and view all the answers

Which of the following accurately describes John Dalton's contribution to atomic theory?

Proposed that matter is made up of indivisible particles known as atoms. Signup and view all the answers

In Thomson's Plum Pudding Model, how are electrons depicted within the atom?

Electrons are situated randomly within a cloud of positive charge. Signup and view all the answers

Which subatomic particle is considered to be neutral and has no charge?

Neutron Signup and view all the answers

What analogy is used in explaining Rutherford's Gold Foil Experiment?

Throwing marbles at paper where most pass through but some bounce back. Signup and view all the answers

Which statement accurately describes molecular compounds?

They involve the sharing of electrons between nonmetals. Signup and view all the answers

What determines the properties of elements in the same group on the periodic table?

The number of valence electrons in the outer shell. Signup and view all the answers

Which of these examples illustrates the characteristics of alkali metals?

They react violently with water. Signup and view all the answers

What is the main characteristic of ionic compounds?

They are created through the attraction of cations and anions. Signup and view all the answers

Which of the following accurately describes the states of matter?

Liquids have a fixed volume but take the shape of their container. Signup and view all the answers

What is the significance of molecular mass in chemical reactions?

It is important for calculating the amount of substance used. Signup and view all the answers

How do the properties of elements change as you move across a period?

They change systematically with each element. Signup and view all the answers

How is atomic mass determined for an element?

It is calculated as the sum of protons and neutrons in the nucleus. Signup and view all the answers

What example illustrates the significance of neutrons in atomic structure?

They are essential for holding the nucleus together. Signup and view all the answers

In what way can isotopes of an element be represented?

Using either hyphen form or nuclide form. Signup and view all the answers

Which correctly describes cations in relation to electron movement?

They are produced by losing electrons. Signup and view all the answers

What characteristic of carbon-14 distinguishes it from carbon-12?

It has more neutrons than protons. Signup and view all the answers

What information does the average atomic mass on the periodic table convey?

It considers the abundance of naturally occurring isotopes. Signup and view all the answers

Which trend in periodic table is associated with the charges of ions?

Group 1 metals usually form cations with a +1 charge. Signup and view all the answers

Which of the following statements about average atomic mass is accurate?

It reflects a weighted average based on isotopic abundance. Signup and view all the answers

What aspect of the atom did Rutherford's Gold Foil Experiment primarily reveal?

The presence of a dense central nucleus containing positive charges Signup and view all the answers

Which subatomic particle has a charge that impacts the overall charge of an atom the most?

Protons, since they are responsible for positive charge and define the element Signup and view all the answers

In Dalton's atomic theory, what misconception might arise regarding the nature of atoms?

Atoms can be divided into smaller particles Signup and view all the answers

Which model effectively illustrates the arrangement of charges within an atom as proposed by Thomson?

Plum Pudding Model, with electrons scattered in a positively charged sphere Signup and view all the answers

What distinguishes ionic compounds from molecular compounds?

Ionic compounds form through attraction between charged ions. Signup and view all the answers

Which of the following statements is true regarding nonmetals and their electron behavior?

Nonmetals tend to form anions by gaining electrons. Signup and view all the answers

How are molecular mass calculations important in chemistry?

They help in calculating the correct ratios for chemical reactions. Signup and view all the answers

Which of the following correctly describes the properties of metals?

Metals exhibit high malleability and ductility. Signup and view all the answers

What characteristic do elements in the same group of the periodic table share?

They have the same number of valence electrons. Signup and view all the answers

What is a common property of Group 17 nonmetals?

They typically carry a -1 charge when forming anions. Signup and view all the answers

What defines the arrangement of elements in periods of the periodic table?

Elements in the same period possess the same number of electron shells. Signup and view all the answers

What is the significance of neutrons in an atomic nucleus?

They assist in stabilizing the nucleus by offsetting proton repulsion. Signup and view all the answers

Which description accurately defines isotopes?

Atoms with the same number of protons but different mass numbers. Signup and view all the answers

What is true about the average atomic mass of an element?

It reflects the weighted average of all naturally occurring isotopes of that element. Signup and view all the answers

Which of the following represents a cation?

Ca2+ produced when calcium loses two electrons. Signup and view all the answers

Which notation correctly represents isotopes of an element using nuclide form?

Carbon-12 as 12/6C. Signup and view all the answers

What best describes the formation of anions?

They are created when atoms gain electrons. Signup and view all the answers

What trend can be observed in relation to ion charges on the periodic table?

Metals in Group 1 usually form ions with a +1 charge. Signup and view all the answers

How does the atomic number (Z) define an element?

It denotes the number of protons within the atom's nucleus. Signup and view all the answers

What does the presence of protons in the nucleus primarily contribute to in an atom?

The atom's mass and positive charge Signup and view all the answers

Which model best explains the structure of an atom according to Thomson's findings?

A sphere of positive charge with negatively charged electrons embedded within Signup and view all the answers

What significant observation did Rutherford make during his Gold Foil Experiment?

Most particles passed straight through without any deflection Signup and view all the answers

In Dalton's atomic theory, how are elements expected to combine to form compounds?

In definite ratios that correspond to whole numbers of atoms Signup and view all the answers

What charge do neutrons carry in an atom, and what implication does this have?

No charge; it stabilizes the nucleus without affecting overall charge Signup and view all the answers

What is the typical charge of Group 17 nonmetals when they form ions?

-1 Signup and view all the answers

Which of the following is a property of metals?

Good conductors of heat and electricity Signup and view all the answers

Which term describes the vertical columns on the periodic table?

Groups Signup and view all the answers

In terms of electron shells, what is true about the elements within the same period of the periodic table?

They possess the same number of electron shells Signup and view all the answers

How is molecular weight calculated, and why is it important?

By summing the atomic masses of atoms, it determines the mass of compounds Signup and view all the answers

What defines the chemical formula of a compound?

It shows the ratio of each element in the compound Signup and view all the answers

What is the primary function of neutrons in the nucleus of an atom?

To hold protons together and stabilize the nucleus Signup and view all the answers

Which of the following statements accurately characterizes the atomic mass of an element?

It reflects the sum of protons and neutrons in the nucleus Signup and view all the answers

How is the average atomic mass of an element calculated?

By taking the weighted average of the masses of all naturally occurring isotopes Signup and view all the answers

Which of the following correctly describes isotopes?

Isotopes can be represented in various forms, including hyphen form and nuclide form Signup and view all the answers

What charge does a chlorine ion carry after gaining one electron?

-1 charge Signup and view all the answers

Which statement accurately describes polyatomic ions?

They contain two or more atoms covalently bonded, carrying an overall charge Signup and view all the answers

What characteristic of isotopes influences their average atomic mass on the periodic table?

The weighted abundance of each isotope in nature Signup and view all the answers

Which of the following elements is most likely to be a metal that forms a +2 cation?

Calcium (Ca) Signup and view all the answers

Study Notes

Atomic Structure

Nucleus: Contains protons (p+) and neutrons (n). Positively charged due to protons.
Example: A carbon atom's nucleus has 6 protons and 6 neutrons.
Electron Cloud: Region surrounding the nucleus, containing negatively charged electrons (e-). Electrons are smaller than protons and neutrons.
Example: The electrons in a helium atom's cloud determine how it bonds with other atoms.
Subatomic Particle Charges:
- Protons: Positive (+) charge
- Neutrons: Neutral (no charge)
- Electrons: Negative (-) charge
Example: The positive and negative charges of protons and electrons balance the atom.

Atomic History

Dalton:
- Atomic Theory: Proposed that matter is composed of indivisible particles called atoms.
- Example: Dalton's theory explained how elements combine in fixed ratios to form compounds.
Thomson:
- Plum Pudding Model: Discovered that atoms contain both positive and negative charges. Imagined the atom as a sphere of positive charge with negatively charged electrons embedded within it.
- Example: Similar to raisin pudding, where the pudding is the positive sphere and the raisins are the negative electrons.
Rutherford:
- Gold Foil Experiment: Used alpha particles to bombard gold foil. Discovered a dense, positively charged nucleus within the atom.
- Example: Most alpha particles passed through the foil, but some bounced back as if hitting a hard object.
Chadwick:
- Neutrons: Discovered the neutron, a neutral particle with a mass similar to a proton. Crucial for holding the nucleus together.
- Example: Protons repel each other; neutrons help balance the nucleus.

Elements

Atomic Number (Z): Number of protons in an atom's nucleus; defines the element.
Example: All carbon atoms have an atomic number of 6.
Atomic Mass: Sum of protons and neutrons in an atom's nucleus.
Example: A carbon atom with 6 protons and 6 neutrons has an atomic mass of 12.

Isotopes

Number of Neutrons: Atoms of the same element can have different numbers of neutrons.
Hyphen and Nuclide Forms: Represent isotopes using hyphen form (e.g., Carbon-14) or nuclide form (e.g., ¹⁴₆C).
Example: Carbon-12 and Carbon-14 are isotopes of carbon.

Calculate Average Atomic Mass

Average atomic mass: Weighted average of the naturally occurring isotopes of an element. Listed on the periodic table.
Example: Carbon has two main isotopes: Carbon-12 (98.9% abundance) and Carbon-14 (1.1% abundance). The calculated weighted average is approximately 12.01 amu.

Ions

Number of Electrons: Atoms can gain or lose electrons to become charged particles called ions.
Cations: Positively charged ions formed when atoms lose electrons. Example: Na⁺
Anions: Negatively charged ions formed when atoms gain electrons. Example: Cl⁻
Example: Sodium loses an electron to become Na⁺. Chlorine gains an electron to become Cl⁻

Polyatomic lons

Polyatomic Ions: lons composed of two or more atoms. Example: OH⁻ (hydroxide).
Trends in Periodic Table Charges*
Metals tend to form positive cations (like metals in group 1).
Nonmetals tend to form negative anions (like nonmetals in group 17). Example Metals form cations (+) like Na⁺ Example nonmetals form anions (-) like Cl⁻

Compounds

Chemical Formulas: Represent a compound showing the ratio of elements. Example: H₂O (water).
Molecular Weight: The sum of the atomic masses of all atoms in a molecule. Crucial for chemical calculations.
Example: Molecular weight of water (H₂O): 2(1.01) + 16.00 ≈ 18.02 amu

Ionic vs. Molecular Compounds

Ionic Compounds: Form from attractions between oppositely charged ions (cations and anions). Typical of metal and nonmetal bonding. Example: Sodium chloride (NaCl)
Molecular Compounds: Form from sharing of electrons between nonmetal atoms. Example: Water (H₂O)

States of Matter

Solids (s): Fixed shape and volume; particles are closely packed and vibrate in fixed positions.
Liquids (l): Take the shape of the container, but have a fixed volume; particles are close together and freely move around each other.
Gases (g): Fill the entire container; particles are far apart and move freely.

Physical vs. Chemical Properties

Physical Properties: Observed or measured without changing the identity of the substance (e.g., color, odor, melting point, boiling point, density).
Chemical Properties: Observed when a substance undergoes a chemical change or reaction, changing its identity (e.g., flammability, reactivity with acids).

Pure Substances

Compounds: Two or more elements chemically combined in a fixed ratio. Example: H₂O, CO₂
Elements: Substances that cannot be broken down into simpler substances. Example: O₂, Fe

Mixtures

Heterogeneous Mixtures: Non-uniform composition throughout, with different components visible (e.g., sand and water).
Homogeneous Mixtures: Uniform composition throughout; components are evenly distributed (e.g., saltwater, air).

Physical vs. Chemical Changes

Physical Change: Changes the form or appearance of a substance but not its chemical composition (e.g., melting ice, boiling water).
Chemical Change: Involves a change in the chemical composition of a substance, resulting in a new substance with different properties (e.g., burning wood, rusting iron).

Law of Conservation of Mass

The mass of the reactants equals the mass of the products in a chemical reaction. Matter is neither created or destroyed.
Example When methane and oxygen react to form carbon dioxide and water, the mass on both sides of the reaction is equal.

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Description

Test your knowledge on atomic structure and the historical development of atomic theory. This quiz covers key concepts such as subatomic particles, their charges, and the contributions of scientists like Dalton and Thomson. Perfect for students learning chemistry basics.