Chemistry Chapter: Atomic Theory and Proportions

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Questions and Answers

What conclusion did he reach about the mass gained by the tree?

The mass gained came from the air.

The mass gained came equally from water and soil.

The mass gained came from the soil.

The mass gained came from the water. (correct)

According to the law of definite proportions, what is the mass ratio of oxygen to hydrogen in water?

1 to 8

4 to 1

2 to 1

8 to 1 (correct)

If there are 16.89 g of magnesium in a sample of MgO, how much oxygen is present?

8.12 g

11.11 g (correct)

14.78 g

19.00 g

What aspect of matter does Dalton’s atomic theory NOT emphasize?

Atoms can be created in reactions. Signup and view all the answers

What does the law of multiple proportions indicate about different compounds of the same elements?

They follow a ratio of small whole numbers. Signup and view all the answers

Which of the following compounds contains the highest mass of oxygen per atom of carbon?

Carbon dioxide Signup and view all the answers

In the formation of nitrogen oxides, what weight of nitrogen combines with 48 g of oxygen?

28 g Signup and view all the answers

What is NOT a component of Dalton's atomic theory?

Atoms can be created from energy. Signup and view all the answers

Which particle has a positive charge and is located in the nucleus of an atom?

Proton Signup and view all the answers

How does the mass of an electron compare to that of a proton?

About 1/1800 the mass of a proton Signup and view all the answers

What is the mass number (A) of an atom if it has 6 protons and 8 neutrons?

14 Signup and view all the answers

What effect does gaining an electron have on an atom?

It becomes a negative ion Signup and view all the answers

Which statement about anions is correct?

They gain electrons Signup and view all the answers

What determines the charge of an atom?

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

What is the atomic number (Z) of an element?

Number of protons Signup and view all the answers

What type of ion is Mg2+?

Cation Signup and view all the answers

What do condensed structural formulas represent?

The details of atom connectivity with less detail Signup and view all the answers

In line-angle formulas, what does an end or intersection of a line typically represent?

A carbon atom Signup and view all the answers

How are elements arranged in the Modern Periodic Table?

By increasing atomic number Signup and view all the answers

What is indicated by the group number in relation to valence electrons?

The number of valence electrons in the outermost orbit Signup and view all the answers

What is a characteristic of elements within the same group of the Periodic Table?

They have similar chemical properties Signup and view all the answers

What is the charge of the magnesium ion represented as Mg2+?

2+ Signup and view all the answers

How many protons are present in a Mg2+ ion?

12 Signup and view all the answers

Which of the following statements about ionic compounds is true?

They are made up of charged particles. Signup and view all the answers

Which of the following represents an empirical formula?

C2H6 Signup and view all the answers

What distinguishes molecular compounds from ionic compounds?

Molecular compounds involve shared electrons. Signup and view all the answers

Which of the following refers to the true number of atoms in a molecule?

Molecular formula Signup and view all the answers

What happens during the formation of an ionic bond?

Electrons are transferred from one atom to another. Signup and view all the answers

How many electrons does a Mg2+ ion possess?

10 Signup and view all the answers

What is the correct name for the compound FeO?

iron (II) oxide Signup and view all the answers

Which of the following correctly represents the formula for copper(II) chloride?

CuCl2 Signup and view all the answers

What is the charge of the ammonium ion?

1+ Signup and view all the answers

Which of the following names corresponds to the ion with the formula CrO4^2-?

chromate ion Signup and view all the answers

How should the compound P2O5 be named?

diphosphorus pentoxide Signup and view all the answers

What is the correct name for the ion SO4^2-?

sulfate ion Signup and view all the answers

What prefix is used to denote three atoms in a compound's name?

tri- Signup and view all the answers

Which of the following is the correct formula for the hypobromite ion?

BrO- Signup and view all the answers

Study Notes

The Law of Definite Proportions

In a chemical compound, the elements are always combined in the same proportions by mass.
For example, water is always composed of 8 parts by mass of oxygen and 1 part by mass of hydrogen.

Dalton’s Atomic Theory

Proposed in 1803 to explain the law of conservation of mass and the law of definite proportions.
Matter is composed of atoms, which are tiny, indivisible particles.
All atoms of a given element are the same, but differ from atoms of other elements.
Compounds are formed when atoms of different elements unite in fixed proportions.
Chemical reactions involve the rearrangement of atoms, no atoms are created, destroyed, or broken apart.

The Law of Multiple Proportions

When two or more compounds of the same two elements are compared, the masses of one element that combine with a fixed mass of the second element are in the ratio of small whole numbers.
Example:
- In Carbon monoxide (CO), 12.0 g of carbon combines with 16.0 g of oxygen.
- In Carbon dioxide (CO2), 12.0 g of carbon combines with 32.0 g of oxygen.
- The ratio of oxygen/carbon in these two compounds is 1:2.

The Modern View of Atomic Structure

The atom has a structure that includes a nucleus and an electron cloud.
The nucleus contains protons and neutrons:
- Protons carry a positive charge.
- Neutrons carry no charge.
The electron cloud contains negatively charged electrons.
Protons and neutrons are much heavier than electrons.

Atomic Notation

Atomic number (Z) is the number of protons in an atom.
Mass number (A) is the sum of protons and neutrons in an atom.
Charge (q) is the difference between protons and electrons (protons - electrons).
The symbol for an element is written as: ^A_ZQ where Z is the atomic number, A is the mass number, and Q is the charge.

Ions

An anion is a negatively charged ion formed when an atom gains electrons.
A cation is a positively charged ion formed when an atom loses electrons.

Molecules and Ions

Molecular compounds involve shared electrons and consist of electrically neutral, discrete particles (molecules).
Ionic compounds involve electron transfer between metals and nonmetals and consist of charged particles (ions).

Chemical Bonds

Covalent bonds involve shared electrons between atoms.
Ionic bonds involve the complete transfer of electrons from one atom to another.

Types of Formulas

Empirical formulas represent the lowest whole number ratio of atoms in a compound.
Molecular formulas show the true number of atoms of each element in the formula of a compound.
Structural formulas show how atoms are attached together and the order in which atoms are bonded.

The Periodic Table

Organizes elements based on increasing atomic number.
Rows are called periods.
Columns are called groups or families.
Elements within a group share similar properties due to similar valence electron configurations.

Naming Compounds

For ionic compounds:
- Name the cation.
- Indicate the charge of the cation using Roman numerals in parentheses.
- Name the anion.
For covalent compounds:
- Use prefixes (mono, di, tri, etc.) to indicate the number of atoms of each element.
- Name the second element using the suffix "-ide".

Identifying Empirical Formulas

An empirical formula represents the simplest whole number ratio of atoms in a compound.
Divide all subscripts in a molecular formula by the greatest common factor to get its empirical formula.

Polyatomic Ions

Consist of multiple atoms with a net charge.
Have specific names that need to be memorized.
Some polyatomic ion names change based on the number of oxygen atoms present.
Use prefixes like "per-", "hypo-", and "-ite" or "-ate" to denote changes in the number of oxygen atoms within the ion.

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Description

Explore the key concepts of Dalton's Atomic Theory and the laws of definite and multiple proportions. This quiz will test your understanding of how elements combine to form compounds and the implications of these laws in chemistry. Dive into the intricacies of matter at the atomic level.