Questions and Answers
Hydrogen makes up 10% of the Earth's crust.
False
The nucleus of an atom contains both protons and electrons.
False
The chemical symbol for sulfur is S.
True
Carbon is present in living organisms at a higher percentage than oxygen.
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Nitrogen is found in the atmosphere at a higher percentage than in living organisms.
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In the formation of an ionic compound, nonmetals always give up electrons.
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Cations are formed when an atom or molecule gains one or more electrons.
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A polar covalent bond is characterized by equal sharing of electrons between atoms.
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Oxygen exhibits higher electronegativity than hydrogen, causing disparity in electron sharing in water.
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Ionic bonds are formed through the sharing of electrons between two atoms.
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Study Notes
Matter and Elements
- Matter consists of substances that cannot be broken down into simpler components called elements.
- Each element is represented by a unique chemical symbol, such as Sulfur (S) and Calcium (Ca).
- The four most prevalent elements in living organisms are Carbon (C), Oxygen (O), Hydrogen (H), and Nitrogen (N).
Elemental Composition in Different Contexts
- Oxygen makes up 65% of human body composition, 21% of the atmosphere, and 46% of Earth's crust.
- Carbon is 18% in human bodies, is present in trace amounts in the atmosphere and Earth's crust.
- Hydrogen constitutes 10% of living organisms, while it's found in trace amounts in the atmosphere and 0.1% in Earth's crust.
- Nitrogen is 3% of human body composition, 78% of the atmosphere, and present in trace amounts in Earth's crust.
Atomic Structure
- An atom is the smallest unit of matter that retains all chemical properties of an element.
- Atoms consist of two main regions: the nucleus (containing protons and neutrons) and the outer region where electrons are located.
- Cations are positively charged ions formed when atoms lose electrons, while anions are negatively charged ions formed when atoms gain electrons.
Chemical Bonding
- Polar Covalent Bonds involve unequal sharing of electrons, leading to partial charges; a prime example is water, where oxygen has a higher electronegativity than hydrogen.
- Carbon serves as a fundamental component of macromolecules (proteins, carbohydrates, lipids, nucleic acids) and can form four covalent bonds with other atoms due to its four outer shell electrons.
Carbon Structures
- Carbon-based molecules can have three primary structural forms: straight chains, branched chains, and ring structures.
- These diverse forms contribute to the complexity and functionality of organic molecules.
Functional Groups
- Functional groups are specific groupings of atoms that impart consistent properties to molecules.
- Each type of macromolecule contains unique functional groups that often interact through hydrogen bonding.
Properties of Water
- Water comprises 60-70% of the human body and is essential for life due to its polarity and ability to form hydrogen bonds.
- Hydrogen bonds are formed between the partial positive charge of hydrogen and the partial negative charge of oxygen in water molecules.
pH Scale and Acids/Bases
- Acids increase H+ concentration in solutions, lowering pH (e.g., HCl → H+ + Cl-).
- Bases decrease H+ concentration, raising the pH (e.g., NaOH → Na+ + OH-).
- pH scale indicates the strength of acids and bases, with strong acids on the lower end (e.g., lemons juice at pH 2) and strong bases on the higher end.
Practice Questions
- Lemon juice (pH 2) has a greater H+ concentration compared to coffee (pH 5).
- The difference in H+ concentration signifies a notable variance in acidity between the two substances.
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Description
Test your understanding of matter, elements, and the properties of subatomic particles such as protons, neutrons, and electrons. This quiz covers essential concepts including atomic charge, mass, and their roles within an atom. Perfect for students of chemistry and related sciences.
