Elements and Compounds in Biology

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Questions and Answers

What is the definition of an element?

A type of molecule that contains two or more atoms

A material that can be broken down into simpler substances

A mixture of different substances

A substance that cannot be divided into other substances (correct)

How many elements are present in nature?

92 (correct)

118

What is the significance of trace elements in living organisms?

They are unnecessary for physiological processes

They are needed in minute quantities for proper physiology (correct)

They are exclusive to non-living matter

They are essential in large quantities for growth

Which statement about matter is true?

Matter is composed of elements and has mass Signup and view all the answers

What is the role of essential elements in living organisms?

They are required for the structure and function of organisms Signup and view all the answers

What is the atomic number of carbon?

6 Signup and view all the answers

Which of the following describes a characteristic of isotopes?

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

What is the mass number of carbon-12?

12 Signup and view all the answers

What keeps electrons near the nucleus of an atom?

The positive charge of protons Signup and view all the answers

Which isotope of carbon is known to be unstable and radioactive?

14C Signup and view all the answers

Which element has the highest percentage by weight in the human body?

Oxygen Signup and view all the answers

What is the term for a substance consisting of two or more different elements combined in a fixed ratio?

Compound Signup and view all the answers

Which of the following statements accurately describes the atomic structure?

Neutrons are electrically neutral. Signup and view all the answers

What is the role of neutrons in an atom?

They affect the mass number. Signup and view all the answers

Which element is NOT classified as one of the primary elements found in living organisms?

Calcium Signup and view all the answers

Which of the following elements is classified as an essential trace element?

Iron Signup and view all the answers

What does the atomic number of an element represent?

The number of protons in the nucleus. Signup and view all the answers

Which compound is composed of sodium and chlorine?

Sodium chloride Signup and view all the answers

What is the result of different arrangements of elements in compounds?

They create unique properties for each compound. Signup and view all the answers

Which of the following is not a property of a proton?

It is electrically neutral. Signup and view all the answers

What distinguishes the different forms of hydrogen mentioned?

The number of neutrons in the nucleus. Signup and view all the answers

Which type of hydrogen contains one neutron?

Deuterium Signup and view all the answers

Which statement is true regarding ordinary hydrogen?

It has no neutrons. Signup and view all the answers

What is the common name for hydrogen that has no neutrons?

Ordinary hydrogen Signup and view all the answers

Which of the following describes deuterium?

It has one neutron in addition to one proton. Signup and view all the answers

What determines the chemical properties of an atom?

The arrangement of electrons in electron shells Signup and view all the answers

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

8 Signup and view all the answers

How do atoms accomplish the achievement of a full outer electron shell?

By sharing, donating, or receiving electrons Signup and view all the answers

How many electrons are required to fill the first electron shell completely?

2 Signup and view all the answers

Which of the following statements is true regarding electron shells?

The third shell can hold more electrons than the second shell Signup and view all the answers

What type of bond results from the sharing or transfer of electrons between atoms?

Chemical bond Signup and view all the answers

In which part of the atom are electrons located?

Surrounding the nucleus in energy levels Signup and view all the answers

Which element has its outer shell filled with 8 electrons, ensuring its stability?

Neon Signup and view all the answers

Study Notes

Elements, Atoms, and Molecules

Living organisms consist of matter; anything that occupies space and has mass.
Matter is composed of chemical elements, which are substances that cannot be broken down.
There are 92 naturally occurring elements, but only a few exist in a pure state.

Essential Elements for Life

Life relies on 25 essential elements, including trace elements needed in minute quantities for growth and physiology.
Major elements by weight percentage in the human body include:
- Oxygen (O): 65.0%
- Carbon (C): 18.5%
- Hydrogen (H): 9.56%
- Nitrogen (N): 3.3%
- Calcium (Ca): 1.5%
- Phosphorus (P): 1.0%
- Potassium (K): 0.4%
- Sulfur (S): 0.3%
- Sodium (Na): 0.2%
- Chlorine (Cl): 0.3%
- Magnesium (Mg): 0.1%
Trace elements include Chromium (Cr), Iron (Fe), Iodine (I), Fluorine (F), and others required in very small amounts.

Compounds Formation

Compounds consist of two or more different elements combined in a fixed ratio.
Example: Sodium chloride (NaCl); a combination of sodium (metal) and chloride (toxic gas) forms an edible compound.
Key biological compounds contain carbon, hydrogen, oxygen, and nitrogen, crucial for structures like DNA.

Atomic Structure

An atom is the smallest unit of matter that retains an element's properties, composed of protons, neutrons, and electrons.
Protons possess a positive charge; electrons have a negative charge; neutrons are neutral.

Atomic Variability

Atoms differ in the number of protons (atomic number), neutrons, and electrons.
For carbon:
- Atomic number: 6 (6 protons).
- Mass number: sum of protons and neutrons (e.g., carbon-12 is written as 12C).
Isotopes exist with the same atomic number but different mass numbers due to varying neutrons (e.g., carbon-14 is radioactive).

Electron Shells

Electrons occupy energy levels called electron shells; chemical properties of an atom depend on the arrangement of these electrons.
The number of electrons influences reactivity; outermost shell electrons dictate chemical behavior.
Atoms aim to fill their outer electron shells via sharing, donating, or receiving electrons, resulting in chemical bonds.

Chemical Bonds

Chemical bonds form due to attractions between atoms when they interact through electron exchanges.
The first electron shell accommodates up to 2 electrons; subsequent shells can hold up to 8 electrons each.
The desire to fill outer shells drives atomic interactions and compound formations.

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Description

This quiz explores the fundamental concepts of elements, atoms, and molecules. Learn about the essential elements for life and their roles in living organisms. Test your knowledge on matter composition and the formation of compounds.