Question

directions: read the following sections. once you have completed the reading, then answer the questions below. hmh science dimensions biology, unit 2, lesson 1, pages 72 - 75 1. what is the relationship between an atom and an element? 2. list the three types of particles that make up an atom. 3. how are atoms held together? explain the differences between the main types of bonding. 4. how does the arrangement of matter change in chemical reactions? 5. the chemical formula for carbon dioxide is co₂. according to the model of this molecule in figure 6 on page 74, what does the number 2 represent?

Explanation:

1. An element is a pure substance made of only one type of atom. All atoms of a particular element have the same number of protons.
2. Protons (positively - charged), neutrons (neutral), and electrons (negatively - charged) make up an atom.
3. Atoms are held together by chemical bonds. Ionic bonds involve the transfer of electrons from one atom to another, creating ions that attract. Covalent bonds involve the sharing of electrons between atoms.
4. In chemical reactions, the atoms of the reactants are rearranged to form products. Chemical bonds are broken and new ones are formed.
5. In the chemical formula $CO_2$, the number 2 represents that there are two oxygen atoms for every one carbon atom in a carbon - dioxide molecule.

Answer:

1. An element consists of only one type of atom.
2. Protons, neutrons, electrons.
3. By chemical bonds. Ionic bonds transfer electrons; covalent bonds share electrons.
4. Atoms of reactants are rearranged as chemical bonds break and new ones form.
5. There are two oxygen atoms per carbon atom in a carbon - dioxide molecule.