Chemistry Elements and Compounds Quiz
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Questions and Answers

What is an element?

Element is the smallest substance of matter. It cannot be broken down into other elements in a chemical reaction.

How many naturally occurring elements are there?

There are 92 (up to Uranium). Everything afterwards is man-made.

What is a compound?

Compounds are made up of 2 or more elements.

What are the four most important elements that make up 96% of life?

<p>Carbon, Oxygen, Hydrogen, and Nitrogen.</p> Signup and view all the answers

What are the three atomic particles of an atom and what are their charges? Where are they located?

<p>In the nucleus - proton (+) and neutron (0). Swimming around the nucleus in orbitals, electrons (-).</p> Signup and view all the answers

What is the mass of a proton and neutron? An electron?

<p>Proton and Neutrons are $1.7 \times 10^{-24}$ kg. An electron is about 1/2000 of an amu.</p> Signup and view all the answers

Are atoms the first characteristic of life?

<p>False (B)</p> Signup and view all the answers

What is the atomic number?

<p>Identifying number of an element. It tells the number of protons.</p> Signup and view all the answers

What is the atomic mass?

<p>Protons + Neutrons; will tell you what the mass is in a mole.</p> Signup and view all the answers

Mass - protons equals?

<p>electrons</p> Signup and view all the answers

All chemical reactions are interactions between what of an atom?

<p>Electrons</p> Signup and view all the answers

What is an isotope?

<p>Isotopes are different atomic forms of an element that have different numbers of neutrons, therefore different masses.</p> Signup and view all the answers

What are hydrogen's three isotopes?

<p>Deuterium (1 neutron), Tritium (2 neutrons).</p> Signup and view all the answers

Where is an electron's potential energy highest?

<p>Electrons are attracted to the nucleus; the farther away from the nucleus, the more potential energy.</p> Signup and view all the answers

What happens when an electron absorbs energy? Loses energy?

<p>Electrons that absorb energy move to a shell away from the nucleus. When it loses energy, it falls back to a shell closer to the nucleus.</p> Signup and view all the answers

Chemical properties are determined by?

<p>Distribution of electrons in the atom's valence shell.</p> Signup and view all the answers

How many orbitals are in the first shell?

<p>1s orbital, which holds 2 electrons.</p> Signup and view all the answers

How many orbitals are in the second energy level?

<p>2 - 1s and 3p orbitals. The s holds 2, the p holds 6, so 8 electrons overall.</p> Signup and view all the answers

How many orbitals are in the third energy level?

<p>3 - 1s, 3p, 5d. The s holds 2, the p holds 6, the d holds 10. Therefore there are 18 possible electrons.</p> Signup and view all the answers

What is a chemical bond?

<p>Interactions that result in atoms staying close together.</p> Signup and view all the answers

What is a covalent bond?

<p>Strong, sharing of a pair of valence electrons by two atoms. Can be single, double, or triple.</p> Signup and view all the answers

What is electronegativity?

<p>It is the tendency to pull electrons to itself. Electronegativity depends on how many electrons are missing and the size of the atom.</p> Signup and view all the answers

What is a non-polar covalent bond?

<p>Equal sharing. These are hydrophobic.</p> Signup and view all the answers

What is a polar covalent bond?

<p>One or more electronegative atoms are more electronegative than others, causing partially positive/negative poles.</p> Signup and view all the answers

What is an ionic bond?

<p>Two atoms are so unequal that their attraction for the valence electron causes the most electronegative atom to strip the electron completely away.</p> Signup and view all the answers

What is a positive ion called? A negative one?

<p>Cation (+), Anion (-).</p> Signup and view all the answers

What compounds do ionic bonds form?

<p>Ionic bonds form crystals called salts. They harden into three-dimensional lattices.</p> Signup and view all the answers

Do compounds have the same properties as their elements?

<p>False (B)</p> Signup and view all the answers

What are two weak chemical bonds?

<p>Hydrogen bonding and Van der Waals forces.</p> Signup and view all the answers

What is a hydrogen bond?

<p>Hydrogen bonding is when a hydrogen atom covalently bonded to one electronegative atom is also attracted to another electronegative atom.</p> Signup and view all the answers

What is the rate of reaction dependent on?

<p>Concentration of reactants, presence of catalysts, temperature.</p> Signup and view all the answers

What is chemical equilibrium?

<p>When the rate of the forward and reverse reactions are the same and the relative concentrations of products/reactants stop changing.</p> Signup and view all the answers

A hydrogen bond is a?

<p>Weak chemical bond.</p> Signup and view all the answers

What is polar covalent in terms of electronegativity?

<p>If the difference is 0.5 to 0.8.</p> Signup and view all the answers

Under what circumstances do two atoms form an ionic bond?

<p>When one is a metal and has extra electrons that it wants to lose, and another is a non-metal that wants to gain electrons.</p> Signup and view all the answers

In hydrogen bonds, it's important to note that?

<p>The two molecules must be polar, the two molecules are already participating in covalent bonds with other molecules, they are transient.</p> Signup and view all the answers

Which of the following statements regarding essential elements and living organisms is true?

<p>Although all forms of life require iron, other elements are required only by certain species. (A)</p> Signup and view all the answers

Evaluate the following statement: Concentrations of trace elements in an environment above what is required by organisms generally has no effect on those organisms.

<p>False. Elevated concentrations of trace elements such as chromium and phosphorus can be toxic. (A), False. Elevated concentrations of some trace elements such as cobalt and chromium can be toxic. (D)</p> Signup and view all the answers

Consider a hypothetical atom with an atomic number of 4 and a net electronic charge of +1. How many neutrons does this atom have?

<p>The answer cannot be determined from the information provided. (B)</p> Signup and view all the answers

Discuss what determines the chemical behavior of an element and why the atoms of some elements have more of a tendency to react chemically than others.

<p>Chemical reactions are all interactions between an atom's valence electrons. The extent of an atom's reactivity is based on the number of valence electrons it has.</p> Signup and view all the answers

Flashcards

Element

A pure substance that cannot be broken down into simpler substances through chemical reactions.

Naturally Occurring Elements

There are 92 naturally occurring elements found in nature, ranging from Hydrogen to Uranium. Elements beyond Uranium are man-made.

Compound

Two or more elements combined in fixed ratios.

Key Biological Elements

Carbon, Oxygen, Hydrogen, and Nitrogen make up 96% of living matter.

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Atom

The smallest unit of an element that retains the chemical properties of that element. It consists of a nucleus and electrons orbiting around it.

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Proton

Positively charged subatomic particles found in the nucleus of an atom.

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Neutron

Neutral subatomic particles found in the nucleus of an atom.

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Electron

Negatively charged subatomic particles that orbit the nucleus of an atom.

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Atomic Number

The number of protons in an atom, represented as a subscript.

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Atomic Mass

The sum of protons and neutrons in an atom, represented as a superscript.

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Isotope

Atoms of the same element with different numbers of neutrons, leading to different mass numbers.

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Protium

The most common isotope of hydrogen, with no neutrons.

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Deuterium

An isotope of hydrogen with one neutron, heavier than protium.

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Tritium

An isotope of hydrogen with two neutrons, radioactive and heavier than deuterium.

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Electron Energy Levels

Electrons farther from the nucleus have more energy and can absorb energy to move to higher energy levels, or release energy to move closer to the nucleus.

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Valence Shell

The outermost shell of an atom, containing valence electrons.

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Stable Atoms

Atoms with filled valence shells are chemically unreactive.

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Ionic Bond

A type of chemical bond formed by the transfer of electrons between atoms, resulting in charged ions.

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Cation

A positively charged ion formed when an atom loses electrons.

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Anion

A negatively charged ion formed when an atom gains electrons.

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Covalent Bond

A type of chemical bond formed by the sharing of valence electrons between atoms.

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Electronegativity

The ability of an atom to attract and hold onto electrons in a chemical bond.

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Polar Covalent Bond

A type of covalent bond where electrons are shared unequally, resulting in partial charges.

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Non-Polar Covalent Bond

A type of covalent bond where electrons are shared equally, resulting in no partial charges.

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Weak Chemical Bonds

Weak bonds, including hydrogen bonds and van der Waals forces, that play important roles in biological systems.

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Chemical Reaction

A process involving the formation and breaking of chemical bonds, transforming reactants into products.

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Chemical Equilibrium

A state in which the rates of the forward and reverse reactions are equal, maintaining constant concentrations of reactants and products.

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Reactivity of Elements

The reactivity of an element is determined by its valence electrons, with atoms having nearly filled or empty valence shells being more reactive.

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Study Notes

Elements and Compounds

  • An element is a pure substance that cannot be broken down into simpler substances through chemical reactions.
  • There are 92 naturally occurring elements, from Hydrogen to Uranium. Elements beyond Uranium are man-made.
  • Compounds consist of two or more elements combined in fixed ratios.

Key Biological Elements

  • The four main elements that make up 96% of living matter are Carbon, Oxygen, Hydrogen, and Nitrogen.

Atomic Structure

  • Atoms consist of three subatomic particles: protons (positive charge) and neutrons (neutral) in the nucleus, while electrons (negative charge) orbit the nucleus.
  • Protons and neutrons have a mass of 1.7 x 10^-24 kg; electrons have a mass approximately 1/2000 of a proton.
  • The atomic number indicates the number of protons in an atom and is represented as a subscript.
  • The atomic mass is the sum of protons and neutrons, indicated as a superscript.

Chemical Reactions and Isotopes

  • Isotopes are variants of an element with different numbers of neutrons, resulting in different masses; they can be stable or radioactive.
  • Hydrogen has three isotopes: protium (no neutrons), deuterium (1 neutron), and tritium (2 neutrons).

Electron Distribution and Chemical Bonds

  • Electrons farther from the nucleus have higher potential energy and can absorb energy to move to higher orbitals (endothermic), or release energy to move closer (exothermic).
  • Chemical properties are determined by electron distribution in the valence shell; atoms with completed valence shells are unreactive.
  • Ionic bonds form when an electron is transferred from one atom to another, resulting in charged ions: cations (+) and anions (-).

Bond Types

  • Covalent bonds involve the sharing of valence electrons and can be single, double, or triple.
  • Electronegativity is an atom's ability to attract and hold onto electrons, influenced by both the number of missing electrons and the atom's size.
  • Polar covalent bonds have unequal sharing of electrons, resulting in partially positive and negative charges, while non-polar covalent bonds exhibit equal sharing.

Weak Bonds and Chemical Reactions

  • Weak chemical bonds include hydrogen bonds (attractions between a hydrogen atom covalently bonded to an electronegative atom and another electronegative atom) and Van der Waals forces.
  • Chemical reactions involve the formation and breaking of bonds, transforming reactants into products.
  • Factors affecting reaction rates include reactant concentration, temperature, and catalysts.

Chemical Equilibrium

  • Chemical equilibrium is achieved when the forward and reverse reaction rates are equal, maintaining constant concentrations of reactants and products.

Special Properties of Elements

  • Carbon, hydrogen, nitrogen, and oxygen comprise 20-25% of living mass.
  • Excess concentrations of trace elements can be toxic, emphasizing the importance of balanced element levels in biological systems.

Determining Reactivity

  • The reactivity of an element is determined by its valence electrons; atoms with nearly filled or nearly empty valence shells tend to be more reactive.
  • Atoms that lose or gain electrons achieve stability through the formation of ionic or covalent bonds, based on the composition of their valence shells.

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Test your knowledge on elements and compounds with this quiz! Discover key biological elements, atomic structure, and chemical reactions. Perfect for students looking to strengthen their chemistry fundamentals.

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