Biology Chapter 2 Homework Flashcards
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Questions and Answers

A substance that cannot be broken down into other substances by ordinary chemical procedures is a(n) _____.

element

Which atom diagram shows the electron with the highest potential energy?

Electrons are held in an atom by attraction to what particle or location?

Attraction to the positively charged protons in the nucleus

What can happen to an electron when sunlight hits it? (Select all that apply)

<p>It can move out to a higher electron shell.</p> Signup and view all the answers

Changing the number of _____ would change an atom into an atom of a different element.

<p>protons in an atom</p> Signup and view all the answers

What type of bond is joining the two hydrogen atoms?

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

A(n) _____ refers to two or more atoms held together by covalent bonds.

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

This atom can form up to _____ single covalent bond(s).

<p>4</p> Signup and view all the answers

A(n) _____ bond joins these two oxygen atoms.

<p>double covalent</p> Signup and view all the answers

The brackets are indicating a(n) _____ bond.

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

What name is given to the bond between water molecules?

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

Atoms with the same number of protons but with different electrical charges _____

<p>are different ions</p> Signup and view all the answers

In salt, what is the nature of the bond between sodium and chlorine?

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

An ionic bond involves _____

<p>an attraction between ions of opposite charge</p> Signup and view all the answers

What type of bond joins the carbon atom to each of the hydrogen atoms?

<p>single (nonpolar) covalent</p> Signup and view all the answers

Covalent bonds hold atoms together because they...

<p>both (a) and (b).</p> Signup and view all the answers

In molecules, C, H, O, and N atoms usually make __, __, __, and __ bonds respectively.

<p>4, 1, 2, 3</p> Signup and view all the answers

An atom's atomic number is 7. Its valence is most likely...

<p>3</p> Signup and view all the answers

By making two covalent bonds, an O atom (with 8 protons) fills its valence shell. Why does the atom's charge stay close to zero?

<p>Shared electrons aren't always near oxygen.</p> Signup and view all the answers

In a double covalent bond, a carbon atom shares...

<p>electrons in two orbitals.</p> Signup and view all the answers

The ammonia molecule in the diagram has the observed bond orientation because...

<p>All of the above.</p> Signup and view all the answers

Without making or breaking bonds, the pictured molecule can change its shape because...

<p>rotation can occur around single bonds.</p> Signup and view all the answers

Two C atoms form a double bond. Each C is bound to two H atoms. Which statement is true?

<p>All the atoms lie in a plane.</p> Signup and view all the answers

Partial charges occur when...

<p>both (a) and (b).</p> Signup and view all the answers

To fill the valence shell, an electrically neutral, unbonded atom with atomic number 8 must add...

<p>2 electrons.</p> Signup and view all the answers

Which answer helps to explain why carbon atoms tend to make 4 covalent bonds?

<p>The valence shell needs 8 electrons.</p> Signup and view all the answers

An electrically neutral molecule has the formula C3H4O2N. If the carbon atoms form the usual number of bonds, how many covalent bonds will each hydrogen atom have with other atoms in the molecule?

<p>1</p> Signup and view all the answers

Chemical equilibrium is reached when _____

<p>the forward and reverse reactions occur at the same rate so that the concentrations of reactants and products remain the same.</p> Signup and view all the answers

The atomic number of sulfur is 16. Sulfur combines with hydrogen by covalent bonding to form a compound, hydrogen sulfide. Based on the number of valence electrons in a sulfur atom, predict the molecular formula of the compound.

<p>H2S</p> Signup and view all the answers

What happens when two atoms form a chemical bond?

<p>A chemical bond forms when two atoms transfer or share outer electrons to complete their outer shells.</p> Signup and view all the answers

Which statement about weak bonds is correct?

<p>Weak bonds are transient and easily reversible.</p> Signup and view all the answers

Study Notes

Elements and Atoms

  • An element is a fundamental substance that cannot be broken down into simpler substances through ordinary chemical procedures.
  • Atoms are held together by the attraction between electrons and positively charged protons in the nucleus.

Electron Behavior

  • Electrons can absorb sunlight, enabling them to move to a higher electron shell or remain in their original shell.
  • When an electron gains energy, it transitions from a lower to a higher shell; losing energy prompts movement from a higher to a lower shell.

Subatomic Particles and Bonds

  • Changing the number of protons in an atom alters it into a different element.
  • Covalent bonds occur when atoms share electrons; for example, two hydrogen atoms form a covalent bond.
  • A molecule is defined as two or more atoms bonded covalently.

Bonding Details

  • An atom can form up to four single covalent bonds and typically forms a double covalent bond with another element like oxygen.
  • Ionic bonds are formed between charged particles like sodium and chlorine, characterized by attraction between ions of opposite charges.

Molecular Structure and Charge

  • Water molecules exhibit hydrogen bonds, responsible for many of water's unique properties.
  • Ions with the same number of protons but different charges are classified as different ions.

Covalent Bonding Characteristics

  • Single covalent bonds involve shared electrons. Carbon usually makes four bonds, while hydrogen, oxygen, and nitrogen typically make one, two, and three bonds, respectively.
  • The atomic number reveals the number of protons; an atom with atomic number 8 needs two additional electrons to complete its valence shell.

Chemical Equilibrium

  • Chemical equilibrium is achieved when forward and reverse reactions occur at the same rate, leading to stable concentrations of reactants and products.

Structural Flexibility

  • Molecules can change shape without breaking bonds due to rotation around single bonds.

Weak Bonds

  • Weak bonds are typically transient and easily reversible, playing a crucial role in molecular interactions.

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Test your knowledge of fundamental concepts from Biology Chapter 2 with these flashcards. Each card focuses on essential terms and definitions including elements and atomic structure. Perfect for review or preparation for exams.

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