Atomic Structure Basics

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Questions and Answers

What is a chemical bond?

A force that pushes electrons out of an atom

A force that binds atoms together (correct)

A force that separates neutrons and protons

A force that repels atoms from each other

What is formed when one or more electrons are transferred from one atom to another?

Hydrogen bond

Covalent bond

Metallic bond

Ionic bond (correct)

Which of the following is NOT a main type of chemical bond?

Metallic bond (correct)

Ionic bond

Covalent bond

Hydrogen bond

What happens to atoms in ionic bonds?

They transfer electrons Signup and view all the answers

What are atoms in compounds held together by?

Chemical bonds Signup and view all the answers

Who first introduced the concept of the atom?

Democritus Signup and view all the answers

Approximately how many sulfur atoms lined up side by side would make a row about a centimeter long?

100 million Signup and view all the answers

What charge do protons carry?

Positive (+) Signup and view all the answers

What is the relative mass of an electron compared to a proton?

1/1840 Signup and view all the answers

What is the maximum number of electrons that the first shell can hold?

Two Signup and view all the answers

Why are atoms electrically neutral?

They have equal numbers of electrons and protons Signup and view all the answers

What is a chemical element?

A pure substance that consists entirely of one type of atom Signup and view all the answers

Which atomic particle defines the atomic number of an element?

Proton Signup and view all the answers

Which elements make up about 99 percent of the mass of living things?

Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorus, Calcium Signup and view all the answers

What are isotopes?

Atoms of the same element with different numbers of neutrons Signup and view all the answers

How does the number of neutrons in isotopes affect their properties?

Neutrons affect atomic mass but not chemical properties Signup and view all the answers

What does the 'weighted average' of isotope masses refer to?

The abundance of each isotope in nature when calculating average mass Signup and view all the answers

What part of an atom is involved in chemical interactions?

Electron shells Signup and view all the answers

Why are trace elements important, despite their small percentage in living organisms?

They are necessary for basic cellular functions Signup and view all the answers

What does the chemical formula $H_2O$ represent?

Two hydrogen atoms and one oxygen atom Signup and view all the answers

How do scientists indicate the composition of compounds?

Using chemical formulas Signup and view all the answers

In what ratio do sodium and chlorine combine in table salt?

1:1 Signup and view all the answers

Which property is true about compounds compared to their constituent elements?

Compounds have different properties from their elements Signup and view all the answers

What happens when hydrogen and oxygen combine?

They form liquid water Signup and view all the answers

What is one use of radioactive isotopes in the field of medicine?

Detecting cancer Signup and view all the answers

Where is the radioactive isotope $131I$ found after being injected into the body?

In the thyroid gland Signup and view all the answers

What is a common characteristic of radioactive isotopes?

They have unstable nuclei Signup and view all the answers

What are the strongest chemical bonds?

ionic and covalent Signup and view all the answers

What is the primary significance of weak interactions within a living cell?

They allow temporary molecular interactions. Signup and view all the answers

What is an example of weak interactions mentioned in the text?

van der Waals forces Signup and view all the answers

What describes van der Waals forces?

Slight attractions between molecules that are very close together. Signup and view all the answers

Under what condition can van der Waals forces be strong enough to hold molecules together?

If the molecules fit against each other with very little space between them. Signup and view all the answers

What can the combined van der Waals forces on the feet of a gecko do?

Help the gecko adhere to surfaces like walls. Signup and view all the answers

What do hydrogen bonds typically form between?

A hydrogen atom of one molecule and an oxygen or nitrogen atom of a neighboring molecule Signup and view all the answers

Why are hydrogen bonds important for understanding water?

They are crucial for the special properties of water. Signup and view all the answers

Study Notes

Atoms

The concept of the atom was first introduced by Greek philosopher Democritus, who called the smallest fragment of any substance an atom, meaning "unable to be cut".
Atoms are incredibly small, with 100 million sulfur atoms placed side by side making a row only about a centimeter long.
Atoms contain subatomic particles, including protons, neutrons, and electrons.

Protons and Neutrons

Protons and neutrons have similar masses, but protons are positively charged, while neutrons have no charge.
Protons and neutrons bind together to form the nucleus at the center of the atom.

Electrons

Electrons are negatively charged particles with a mass of about 1/1840 that of a proton.
Electrons are in constant motion in the space surrounding the nucleus and are arranged in shells or orbitals.
The first shell can hold up to two electrons, and the second shell can hold up to eight electrons.

Elements and Isotopes

A chemical element is a pure substance consisting of one type of atom.
Elements are represented by one or two-letter symbols, such as C for carbon and H for hydrogen.
The number of protons in the nucleus of an element is called its atomic number.
Isotopes are atoms of the same element with different numbers of neutrons, such as carbon-14 with 8 neutrons.

Chemical Compounds

Chemical compounds are substances formed by the chemical combination of two or more elements in definite proportions.
Chemical formulas, such as H_2O for water and NaCl for table salt, show the composition of compounds.
The physical and chemical properties of a compound are usually different from those of the elements from which it is formed.

Radioactive Isotopes

Some isotopes are radioactive, meaning their nuclei are unstable and break down at a constant rate over time.
Radioactive isotopes have important scientific and practical uses, such as determining the ages of rocks and fossils.

Chemical Bonds

Chemical bonds are the attractive forces that bind atoms together.
The main types of chemical bonds are ionic bonds and covalent bonds.

Weak Interactions

Weak interactions, such as van der Waals forces, are important in the chemistry of living things.
Van der Waals forces produce a slight attraction between molecules when they are very close together.

Hydrogen Bonds

Hydrogen bonds are a form of weak interaction between a hydrogen atom of one molecule and an oxygen or nitrogen atom of a neighboring molecule.
Hydrogen bonds are essential to understanding the special properties of water.

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Description

Learn about the fundamental unit of matter, the atom, and its properties. Discover the concept of atoms and its history, size, and characteristics.