Unicorn
What is a mixture?
a substance made by mixing substances together.
Aristotle and Democritus aren’t scientists. What were they?
Philosiphers
The outermost shell when stable it is what type of element?
noble gas
What is atomic number?
the number of protons in the nucleus of an atom,
Metalloids have the appearance of what and properties of what?
Appearance of metals and proporties of non metals
What are the types of mixtures? What is the difference?
heterogeneous and homogeneous. Heterogeneous mixtures have visually distinguishable components, while homogeneous mixtures appear uniform throughout.
Name of scientist of the cathode-ray experiment?
physicist J.J. Thomson
What is the octet rule?
The octet rule states that atoms tend to form compounds in ways that give them eight valence electrons
Can we predict the properties of undiscovered elements?
Yes
What is oxidation number?
a number assigned to an element in chemical combination which represents the number of electrons lost (or gained, if the number is negative), by an atom of that element in the compound.
What is some evidence that a chemical reaction is occurring?
What is some evidence that a chemical reaction is occurring?
What was Aristotle’s idea about the components of the atom?
He thought that all materials on Earth were not made of atoms, but of the four elements, Earth, Fire, Water, and Air.
What is the difference between ions and atoms.
Atoms are neutral; they contain the same number of protons as electrons. By definition, an ion is an electrically charged particle produced by either removing electrons from a neutral atom to give a positive ion or adding electrons to a neutral atom to give a negative ion.
What are isotopes?
Each of two or more forms of the same element that contain equal numbers of protons but different numbers of neutrons in their nuclei, and hence differ in relative atomic mass but not in chemical properties; in particular, a radioactive form of an element.
What is ionization potential?
the amount of energy required to remove an electron from an isolated atom or molecule.
What is the difference between a law and a theory?
a law predicts what happens while a theory proposes why. A theory will never grow up into a law. Theories change, laws don't
Explain Rutherford’s discovery of the nucleus. What did he expect and what happened. What did that prove?
Rutherford aimed tiny positive alpha particles at a thin sheet of gold foil. (An alpha particle, like a helium nucleus, has 2 protons and 2 neutrons.) He then measured how much the gold foil defl ected the particles by surrounding the foil with a fl uorescent screen. Th e screen glowed where the particles hit it. Rutherford made a prediction based on Th omson’s model: if the electrons were equally distributed throughout the atom, the positively charged alpha particles should pass straight through the atoms of the foil. Th ey would not be deflected (Figure 6(a)). After extensive trials, Rutherford observed that most of the alpha particles did indeed pass through the gold foil unaffected. However, a few particles were deflected at large angles. Rutherford was amazed by his observations. He famously declared “it was almost as incredible as if you fired a 15-inch shell at a piece of tissue paper and it came back and hit you.” From these observations, Rutherford reasoned that each atom contained a small, dense, positively charged central nucleus
What is mass spectroscopy?
Scientists use mass spectroscopy to identify isotopes present in samples.
Who is john new land? What did he do?
He arranged the known elements in order of increasing atomic weight, and found that elements with similar properties occurred at regular intervals. He divided the elements into seven groups of eight, in what he later called the 'law of octaves'.
What is electron affinity?
Electronegativity is a measure of an atom's ability to attract shared electrons to itself.
What is an example of allotropic?
The term allotrope refers to one or more forms of a chemical element that occur in the same physical state. ... For example, graphite and diamond are both allotropes of carbon that occur in the solid state. Graphite is soft, while diamond is extremely hard.
Explain what Dalton’s Atomic Theory proposes.
all matter is made up of tiny, indivisible particles called atoms • all atoms of an element are identical • atoms of different elements are different • atoms are rearranged to form new substances in chemical reactions, but they are never created or destroyed
How to calculate the average atomic mass?
m1p1 + m2p2
What did Antoine-Laurent first to invent?
He established the law of conservation of mass, determined that combustion and respiration are caused by chemical reactions with what he named “oxygen,”
Why is it called halogen?
They were given the name halogen, from the Greek roots hal- (“salt”) and -gen (“to produce”), because they all produce sodium salts of similar properties