You are allowed to offset capital gains with capital losses. If you have capital gains equal to or more than the stock loss, then it is fully deductible. If you have no other capital gains or the loss exceeds the capital gains is limited to the lessor amount of the loss that exceeds the gain or $3,000 (1,500 if your filing as married filing separate status). If the loss is limited in the current year, you may carry over the unused amount into future years until it is completely used up.

Is the loss I incurred from buying and selling the same 100 shares of stock in the same day deductible?

The tax laws "wash sale" provisions prohibit you from recognizing any loss from the sale of buying and selling substantially the same stock within 30 days of selling a stock. If you incur a gain within the 30 day period the "wash sale" provisions do not apply and gain is reportable on IRS Schedule D.

Are the employee stock options I just received taxable on my tax return?

No. If your stock option is granted under a employee stock option plan, the granting or exercise of the option is not included as income on your tax return. You will report either the income or loss on IRS Schedule D when you sell the stock that you purchased by exercising the option. Speak to your local CPA about the tax strategies with your options.