Which is true? (1 point)
A. Electrons are mixed mostly evenly within atoms.
B. Electrons orbit in fixed places around the nuclei of atoms.
C. Electrons move not entirely predictably in electron clouds around the nuclei of atoms.
D. Electrons usually carry a positive charge.
A pure substance can be which of the following?(1 point)
A. a solution
B. a heterogeneous mixture
C. a compound
D. a homogeneous mixture
C. a compound
Which is true? (1 point)
A. Electrons are mixed mostly evenly within atoms.
B. Electrons orbit in fixed places around the nuclei of atoms.
C. Electrons move not entirely predictably in electron clouds around the nuclei of atoms.
D. Electrons usually carry a positive charge.
C. Electrons move not entirely predictably in electron clouds around the nuclei of atoms.
To determine which statement is true about the distribution of electrons within atoms, we need to understand the structure of an atom. The correct statement is as follows:
C. Electrons move not entirely predictably in electron clouds around the nuclei of atoms.
Explanation: According to the current model of the atom, known as the electron cloud model or the quantum mechanical model, electrons do not follow fixed paths like the planets orbiting the Sun (option B). Instead, electrons are described as existing in regions around the nucleus called electron clouds or orbitals. These electron clouds represent the probability of finding an electron in a particular region around the nucleus. However, the movements and positions of electrons within these clouds are not entirely predictable, but rather governed by the principles of quantum mechanics (option C).
Now, let's move on to identifying which of the given options could represent a pure substance:
A pure substance can be:
C. a compound
Explanation: A pure substance is a type of matter that consists of only one type of particle, whether it be an element or a compound. A compound is made up of two or more different elements chemically bonded together in fixed ratios. For example, water (H2O) is a compound composed of hydrogen and oxygen. Therefore, option C, a compound, represents a pure substance.
The other options do not represent pure substances:
A. a solution: A solution is a mixture of two or more substances that are evenly distributed at the molecular level. Therefore, it is not a pure substance.
B. a heterogeneous mixture: A heterogeneous mixture consists of two or more distinct phases or regions with different compositions. It is not uniform or evenly distributed throughout, so it does not qualify as a pure substance.
D. a homogeneous mixture: A homogeneous mixture, also known as a solution, is a mixture that has a uniform composition throughout. It is composed of two or more substances but is not considered a pure substance because it doesn't consist of just one type of particle.