If a carbon atom can form four covalent bonds, it also has four valence electrons. For neutral atoms, the number of valence electrons the same as an atom's main group number.
In a water molecule, the oxygen atom and hydrogen atoms share electrons in covalent bonds, but the sharing is not equal. In the covalent bond between oxygen and hydrogen, the oxygen atom attracts electrons a bit more strongly than the hydrogen atoms.
Answer:
Galileo: "Father of Modern Science."
Aristotle: Geocentric theory." (The planests revolves around the earth.)
Torricelli: Invented the barometer. (An instrument which measures pressure.)
Copernicus: Heliocentric theory. (Aka, the planets revolves around the sun.)
Vesalius: Examined the inner workings of the human body
Newton: Developed law of universal gravitation.
Nightingale: Founded nursing profession.
Celsius: Developed metric temperature scale
I hope this helps! Thanks:)