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</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</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.</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.</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.</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

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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