What is an element?
A pure substance containing one type of atom that cannot be broken down into simpler substances.
By the mid-1800s, what unique constituent did scientists assign to each element?
A unique type of atom.
How did mid-1800s scientists model atoms, and how did they differ?
As tiny, indivisible balls differing only in mass.
What are the two classifications of matter?
Pure substances and mixtures.
Which particles are in the nucleus, and which surround it?
Protons and neutrons are in the nucleus; electrons surround it.
What does an element’s atomic number identify?
The element.
What distinguishes isotopes of the same element by their subatomic particle counts?
They have different neutron counts but the same proton and electron counts.
Why do scientists use atomic models?
Atoms are too small to observe directly.
What determines whether atoms belong to the same element?
They have the same number of protons.
Why is an atom’s mass in unified atomic mass units not identical to its proton and neutron masses?
The atom’s mass also includes the small mass of its electrons.
Answer 10 questions on Atomic Structure and Isotopes.
1. A sample is a pure substance that cannot be broken down into simpler substances and contains just one type of atom. What is the sample classified as?
2. Equal amounts of magnesium, zinc, and copper are separately placed in hydrochloric acid. Which observation indicates the strongest reaction?
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