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Questions and Answers
What is a chemical bond?
What is a chemical bond?
- A force that pushes electrons out of an atom
- A force that binds atoms together (correct)
- A force that separates neutrons and protons
- A force that repels atoms from each other
What is formed when one or more electrons are transferred from one atom to another?
What is formed when one or more electrons are transferred from one atom to another?
- Hydrogen bond
- Covalent bond
- Metallic bond
- Ionic bond (correct)
Which of the following is NOT a main type of chemical bond?
Which of the following is NOT a main type of chemical bond?
- Metallic bond (correct)
- Ionic bond
- Covalent bond
- Hydrogen bond
What happens to atoms in ionic bonds?
What happens to atoms in ionic bonds?
What are atoms in compounds held together by?
What are atoms in compounds held together by?
Who first introduced the concept of the atom?
Who first introduced the concept of the atom?
Approximately how many sulfur atoms lined up side by side would make a row about a centimeter long?
Approximately how many sulfur atoms lined up side by side would make a row about a centimeter long?
What charge do protons carry?
What charge do protons carry?
What is the relative mass of an electron compared to a proton?
What is the relative mass of an electron compared to a proton?
What is the maximum number of electrons that the first shell can hold?
What is the maximum number of electrons that the first shell can hold?
Why are atoms electrically neutral?
Why are atoms electrically neutral?
What is a chemical element?
What is a chemical element?
Which atomic particle defines the atomic number of an element?
Which atomic particle defines the atomic number of an element?
Which elements make up about 99 percent of the mass of living things?
Which elements make up about 99 percent of the mass of living things?
What are isotopes?
What are isotopes?
How does the number of neutrons in isotopes affect their properties?
How does the number of neutrons in isotopes affect their properties?
What does the 'weighted average' of isotope masses refer to?
What does the 'weighted average' of isotope masses refer to?
What part of an atom is involved in chemical interactions?
What part of an atom is involved in chemical interactions?
Why are trace elements important, despite their small percentage in living organisms?
Why are trace elements important, despite their small percentage in living organisms?
What does the chemical formula $H_2O$ represent?
What does the chemical formula $H_2O$ represent?
How do scientists indicate the composition of compounds?
How do scientists indicate the composition of compounds?
In what ratio do sodium and chlorine combine in table salt?
In what ratio do sodium and chlorine combine in table salt?
Which property is true about compounds compared to their constituent elements?
Which property is true about compounds compared to their constituent elements?
What happens when hydrogen and oxygen combine?
What happens when hydrogen and oxygen combine?
What is one use of radioactive isotopes in the field of medicine?
What is one use of radioactive isotopes in the field of medicine?
Where is the radioactive isotope $131I$ found after being injected into the body?
Where is the radioactive isotope $131I$ found after being injected into the body?
What is a common characteristic of radioactive isotopes?
What is a common characteristic of radioactive isotopes?
What are the strongest chemical bonds?
What are the strongest chemical bonds?
What is the primary significance of weak interactions within a living cell?
What is the primary significance of weak interactions within a living cell?
What is an example of weak interactions mentioned in the text?
What is an example of weak interactions mentioned in the text?
What describes van der Waals forces?
What describes van der Waals forces?
Under what condition can van der Waals forces be strong enough to hold molecules together?
Under what condition can van der Waals forces be strong enough to hold molecules together?
What can the combined van der Waals forces on the feet of a gecko do?
What can the combined van der Waals forces on the feet of a gecko do?
What do hydrogen bonds typically form between?
What do hydrogen bonds typically form between?
Why are hydrogen bonds important for understanding water?
Why are hydrogen bonds important for understanding water?
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Study Notes
Atoms
- The concept of the atom was first introduced by Greek philosopher Democritus, who called the smallest fragment of any substance an atom, meaning "unable to be cut".
- Atoms are incredibly small, with 100 million sulfur atoms placed side by side making a row only about a centimeter long.
- Atoms contain subatomic particles, including protons, neutrons, and electrons.
Protons and Neutrons
- Protons and neutrons have similar masses, but protons are positively charged, while neutrons have no charge.
- Protons and neutrons bind together to form the nucleus at the center of the atom.
Electrons
- Electrons are negatively charged particles with a mass of about 1/1840 that of a proton.
- Electrons are in constant motion in the space surrounding the nucleus and are arranged in shells or orbitals.
- The first shell can hold up to two electrons, and the second shell can hold up to eight electrons.
Elements and Isotopes
- A chemical element is a pure substance consisting of one type of atom.
- Elements are represented by one or two-letter symbols, such as C for carbon and H for hydrogen.
- The number of protons in the nucleus of an element is called its atomic number.
- Isotopes are atoms of the same element with different numbers of neutrons, such as carbon-14 with 8 neutrons.
Chemical Compounds
- Chemical compounds are substances formed by the chemical combination of two or more elements in definite proportions.
- Chemical formulas, such as H_2O for water and NaCl for table salt, show the composition of compounds.
- The physical and chemical properties of a compound are usually different from those of the elements from which it is formed.
Radioactive Isotopes
- Some isotopes are radioactive, meaning their nuclei are unstable and break down at a constant rate over time.
- Radioactive isotopes have important scientific and practical uses, such as determining the ages of rocks and fossils.
Chemical Bonds
- Chemical bonds are the attractive forces that bind atoms together.
- The main types of chemical bonds are ionic bonds and covalent bonds.
Weak Interactions
- Weak interactions, such as van der Waals forces, are important in the chemistry of living things.
- Van der Waals forces produce a slight attraction between molecules when they are very close together.
Hydrogen Bonds
- Hydrogen bonds are a form of weak interaction between a hydrogen atom of one molecule and an oxygen or nitrogen atom of a neighboring molecule.
- Hydrogen bonds are essential to understanding the special properties of water.
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