Answer:
- <em><u>Mendeleev produced the first orderly arrangement of known elements.</u></em>
- <em><u>Mendeleev used patterns to predict undiscovered elements.</u></em>
Explanation:
- <u>Mendeleev produced the first orderly arrangement of known elements and used patterns to predict the undiscovered elements.</u>
Those two statments are true.
For the time being there were some 62 known elements. Before Medeleev some schemes to order part of the elements were proposed, but Medeleev showed the relationship between the atomic mass and the properties of the elements (supports second choice). This arrangement is known as the periodic table.
More importantly, Mendeleev predicted correctly the existance and properties of unknown elements, which is his major contribution: he left blanket spaces which where gradually filled when new elements where discovered (this supports the fourth choice).
The first modern chemistry book was written by Antoine Lavoisier (this discards first option).
Mendeleev ordered the elements by increasing mass number (this discards third choice), which was corrected later by the scientist Henry Moseley, who ordered the elements by increasing atomic number (number of protons).
Isotopes were not known by Mendeleev times, so this discards the last option.
An apple should be cut into 4 equal pieces, then put each slice in a separate container and label accordingly with letters A, B, C, and Control. Put water, ginger ale, and lemon juice into containers A, B, and C respectively but leave the Control untouched. Observe which of the slices in containers A, B, C will stay the same color after the one in control turns brown, if the slice maintains its color then the liquid added prevents an apple slice from browning. The variables are the liquids added and the control is the slice that did not have anything added to it.
Answer:
The correct answer is b polar covalent
Explanation:
When two atoms joined by covalent bond has difference in their electronegativities at that time polarity arise.
When the electronegativity difference is low such as 1.3 then the polar bond formed by the two atoms are called polar covalent bond.For example H2O
on the other hand polar bond formed by two atoms having high difference in their electronegativities is called ionic bond.For example NaCl.
