Atomic Theory Overview

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Questions and Answers

Identify the group on the periodic table that contains elements with 7 electrons in their outer shell.

Group 7 (Halogens)

What is the valency of elements in Group 5?

Name a property shared by all elements in Group 0 (Noble Gases).

They are all gases at room temperature.

Explain why Alkali Metals are stored under oil.

Alkali metals are extremely reactive and readily react with oxygen and water in the air, forming oxides and hydroxides. Storing them under oil prevents them from reacting. Signup and view all the answers

What is the general chemical reaction that occurs when an alkali metal reacts with water?

Reactive metal + water → metal hydroxide + hydrogen gas Signup and view all the answers

Briefly describe a physical property that distinguishes Halogens from Noble Gases.

Halogens have low melting and boiling points, meaning they can exist as solids, liquids, or gases at room temperature. Noble gases are all gases at room temperature. Signup and view all the answers

What is the main reason for the chemical inertness of Noble Gases?

They have a full outer shell of electrons (except for Helium). Signup and view all the answers

How does the reactivity of Alkali Metals compare to that of Alkaline Earth Metals?

Alkali metals are more reactive than Alkaline Earth Metals. Signup and view all the answers

What is the main purpose of the periodic table?

To show trends in the physical and chemical properties of elements. Signup and view all the answers

How are elements organized in periods and groups in the periodic table?

Elements are arranged horizontally in periods and vertically in groups. Signup and view all the answers

What does the term 'valency' refer to in terms of elements?

Valency refers to the number of chemical bonds an element can form. Signup and view all the answers

What is the significance of the 'octet rule' in atomic theory?

The octet rule suggests that most atoms aim to have eight electrons in their outer shell when bonding. Signup and view all the answers

How do you determine the valency of an element using its group number?

The valency of an element is equal to its group number for groups 1 to 4, and can be calculated as 8 minus the group number for groups 5 to 8. Signup and view all the answers

What happens to an atom when it loses an electron?

It becomes a positive ion (cation). Signup and view all the answers

Describe how to calculate the relative atomic mass (Ar) of an element with two isotopes.

Multiply the percentage of each isotope by its mass number, sum them, and divide by 100. Signup and view all the answers

If a dipositive ion, M2+, has 25 electrons, what is its atomic number?

The atomic number is 27. Signup and view all the answers

What are isotopes?

Isotopes are variants of an element that have the same number of protons but different numbers of neutrons. Signup and view all the answers

How many electrons does an aluminium ion, 27 3+, have?

It has 10 electrons. Signup and view all the answers

Explain why relative atomic masses are rarely whole numbers.

Relative atomic masses are averages that account for the different isotopes and their abundances. Signup and view all the answers

Define mass number.

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

Calculate the relative atomic mass of gallium given 60.1% gallium–69 and 39.9% gallium–71.

The relative atomic mass of gallium is 70.09. Signup and view all the answers

What is the atomic number and how is it defined?

The atomic number is the number of protons in an atom's nucleus, which defines the element. Signup and view all the answers

Define relative atomic mass.

Relative atomic mass is the weighted average mass of an element's isotopes compared to one-twelfth of the mass of a carbon-12 atom. Signup and view all the answers

What is the unique property of mercury (Hg) at room temperature compared to other metals?

Mercury is the only metal that is liquid at room temperature. Signup and view all the answers

Define isotopes and provide an example.

Isotopes are atoms of the same element with the same atomic number but different mass numbers due to varying numbers of neutrons. An example is carbon, which has isotopes like $^{12}{6}C$ and $^{14}{6}C$. Signup and view all the answers

What defines a metal based on electron behavior?

A metal is defined as any element that loses electrons to form a positive ion, or cation. Signup and view all the answers

How is mass number calculated for an atom?

Mass number is calculated by adding the number of protons and neutrons in the nucleus of an atom. Signup and view all the answers

What are the three sub-atomic particles that make up an atom?

Protons, neutrons, and electrons. Signup and view all the answers

Explain why all atoms are neutral.

All atoms are neutral because they have an equal number of protons and electrons, balancing the positive and negative charges. Signup and view all the answers

What information does the atomic number (Z) provide?

The atomic number indicates the number of protons in an atom. Signup and view all the answers

Define relative atomic mass number (Ar).

The relative atomic mass number is the average mass of all known isotopes of an element, usually expressed as a decimal. Signup and view all the answers

Study Notes

Atomic Theory

Atomic structure consists of protons, neutrons and electrons
Protons and neutrons are located in the atom's nucleus
Electrons orbit the nucleus
Atoms are neutral because the number of protons equals the number of electrons
The number of protons defines the element
Atomic number identifies the element
Isotopes have same number of protons but different number of neutrons
Mass number is the sum of protons and neutrons
Relative atomic mass (Ar) is the average mass of all isotopes, taking into account their natural abundance
Relative molecular mass (Mr) is the sum of the Ar values of all atoms in a molecule
Elements are arranged in the periodic table by increasing atomic number
Elements in the same group have similar chemical properties due to the same number of valence electrons
Elements in the same period have same number of electron shells
Metals tend to lose electrons to form positive ions(cations)
Non-metals tend to gain electrons to form negative ions(anions)
The periodic table shows trends in the physical and chemical properties of elements

Equations

Metal + Oxygen → Metal Oxide
Metal + Water → Metal Hydroxide + Hydrogen

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Description

Explore the fundamental concepts of atomic theory in this quiz. Learn about atomic structure, the role of protons, neutrons, and electrons, and how elements are identified and organized in the periodic table. Test your understanding of key terms like isotopes and atomic mass.